A few questions about how DirecTV Streaming *really* works

That’s a great idea to use the DIRECTV STREAM Osprey Box rather than any ordinary streaming device, that will still give you the traditional cable/satellite feel. The remote itself is very responsive and has a ‘Guide’ button, you can easily choose channels with their numbers (same channel numbers as DIRECTV satellite), and overall the experience is much better.

Now, to your questions.

Yes, unlimited storage cloud DVR will function the same as an in-home DVR. The only difference here is that your content is stored on ‘DIRECTV’s’ server hard drives rather than your own receiver’s internal hard drive. Additionally, recordings DO expire after 9 months.

Yes, the cloud DVR can record whatever is being aired and that you subscribe to. The only case where this could be a problem would be sporting events. Currently, the DIRECTV STREAM service ‘extend sporting events’ feature is yet to be perfected since sometimes it works but other times it doesn’t. For example, if a sporting event runs one hour over it’s expected time, the cloud DVR may not record that extra hour. So, it is the user’s responsibility to record the program(s) airing after the sporting event so that they can retain the additional hours of the event.

With the cloud DVR, you do NOT have access to  auto-skipping the commercials. You can, however, fast forward at your leisure.

I personally haven’t heard of a delay switching channels, especially with the DIRECTV STREAM Osprey Box. I have heard of those using streaming devices (Fire Sticks usually) that sometimes seem to delay a bit or struggle at times. It really depends on your internet connection (wired via Ethernet or wireless) as well as the generation streaming device you are using.

Local channels are integrated right into the Guide. You can easily access them with the channel number (on DIRECTV STREAM box).

You CAN DVR local channels with cloud DVR.

Your last two questions don’t apply to me but I can tell you that many have an easy transition and found the streaming service to be especially beneficial for when they go places. 

The streaming service could sometimes have issues with sporting events recordings (as alluded to earlier) and you need a static IP for DIRECTV STREAM ( one that doesn’t change over time as this caused the service to believe that you weren’t in your home location). 

• DIRECTV offers refurbished boxes for half the price of a new one
• You can try it for five days using In-App Purchases on a FireTV or a Roku
• I used to be on satellite but my new condo's HOA doesn't allow dishes on the roof anymore so I switched to STREAM 3 years ago. It's been lovely as the remote is basically the same, plus nice features like Google Voice integration
• Avoid any convoluted home network setup - the more complicated it is, the more complicated it is to troubleshoot 
• Be aware that this is a streaming service and depends on a reliable internet connection
• Another recommendation is when you sign up for it, use a separate email address so your account doesn't get messed up between Satellite - STREAM. That is not my case, but I've read some other customers complaining/recommending this.

I don't have experience with the satellite service, but a few comments and caveats related to your questions:

• If you "hit record" while watching, the recording starts then, not when you started watching.  But you can watch the recording while it is still recording, if that is desired.  That's generally not needed on most devices - they implicitly record starting when you switch to a channel, and you can pause/rewind/fast forward.  This "recording" is at most 1 hour and will be lost if you switch channels, so that might be a reason to switch to the recording - unfortunately, you can currently only do that by going through the "recordings library", not through the program guide.
• The cloud DVR is indeed a true DVR, with the advantage that you can record effectively unlimited different programs at the same time.  However, their programming capabilities are somewhat primitive.  As noted, you can't manually extend the programming time before or after the scheduled time.  In some cases they will automatically extend the recording as necessary, but this is limited to some sports programming and is apparently not completely reliable even for that.  And this doesn't help for the programming following an extended program.  Support for recording series is problematic.  You can't specify which channel for programs that appear on several, so it might record multiple - this is especially a problem for recording reruns.  You can in theory specify "only new", but this doesn't always work correctly.  You are limited to a maximum of 30 episodes of any show, so picking up extraneous copies can be a problem.  Their mechanisms for managing and finding things in the recording library is also pretty primitive - not a problem if you don't have a lot of things recorded, but could be if you have a lot.  There is hope that improvements in all this will come at some point.
• I have never experienced it, but there have been reports that they in some cases replace a recording with an on-demand item, in which case you can't FF through commercials.  I don't know if this is true or was just users accidentally selecting an on-demand item rather than their recording (perhaps by using the search feature).
• Changing channels isn't instantaneous, but shouldn't take more than a couple of seconds.  Because of the nature of streaming, they only send you the channel you select, so when you change, you are effectively sending them a command to start sending the new channel, and there is a brief time until that happens and the new stream syncs up.
• Depending on where you are and which local channels you currently get, you may get fewer.  To find what you should expect to get, you should check on their lookup tool for your location.   Go here, and select the Regional Sports and Local tab.  This will also show which RSNs you would get.  Note that for RSNs, they generally don't supply alternate feeds and overflows, just the main feed.
• The comment about a static IP address is because the mechanism they use to determine your "home" location is flawed and depends on your IP address not changing.   (This should only be an issue if you have more than 2 TVs actively using the service at the same time at your home, but ther are reports of users having issues with less.)  Whether your address changes depends on your ISP - some rarely if ever change the address (AT&T seems to be in this category), while others do (at least potentially) fairly frequently.  Forcing a user to get a static address is not reasonable, but using the service with some ISPs is apparently a major problem without one (and getting one is a problem with some and is an added for all).  Unfortunately, it may be difficult to know in advance if you will have a problem.  As I said, AT&T as the ISP seems to not, while it appears using a fixed wireless service often has the problem.  I don't know about others.