I left BB as well, or will be. My N4 should be here today. I did try a droid phone once before, and hated it but it was the first generation. Jumping ship for the same reason as you folks, lack of apps and support. I know the lack of physical keyboard is going to be an adjustment. Since you've had some hands on time anything you care to share with a noob? I'm on verizon, so I know there is no root at this time.
The lack of a keyboard isn't a factor for me as the last phone that I had that had a keyboard was the Torch and I barely ever used it.
Some thoughts:
Screen Size - I do a lot of work from my phone and having the big screen + the high resolution is definitely a step up considering I have reading glasses.
Apps - So even though there was Android Runtime for BB that was supposed to give BB users access to Android Apps, more often than not the app once loaded would not work as designed ie limited functionality if not all out failure. Now everything works as it should.
S Pen - Use it...for everything that you can so you know what it can do. It may seem gimmicky at first but I use it at times when using my finger would suffice just to keep my screen smudge free. I find it pretty useful for swype typing even. The bonus is that I can remote in to my desktop and the S Pen acts as a mouse for the cursor in the Windows environment.
Email - I definitely miss the hub on my Z10. It felt more a part of the OS than the Samsung Email does. There was never any lag or delay when going to emails or any other messages in the hub as it was always active. It's not that the email experience on Android is bad, it's just not as efficient as it was on my BB. The Cascades experience with attachments from the hub on BB was superior as well. The hub and how BB handles messaging would be the one thing I would love to see copied.
Touchwiz - Not having owned another Android device, I can't say yet if it is good, bad, or somewhere in between. I figure I should spend the time getting to know it before test driving another launcher. I find it interesting that some people report "no lag" as that is not my experience so far. It's not everywhere and it isn't intolerable, but it's there. I would say the 2 places I find it annoying are when opening the email app (see above) and when wanting to review the picture last taken with the camera.
Settings - As with the S Pen, explore the settings. There is a lot there that will allow you to tailor your user experience with the phone to your liking. Additionally, there are lots of websites/forums/videos with tips and tricks for this phone that are worth checking out. One thing I will mention here is that I found the finger print scanner as a unlock for the phone unreliable and disappointing. I would have loved it had they gotten this right.
Rooting - Again, I want to get to know the phone as it was intended before I start messing with this but knowing myself this may be in my future...
Overall, I am really happy with the phone; I wouldn't have kept it if I wasn't. Some of my points above aren't meant to be nit picky, just some thoughts from my perspective coming from a different device that isn't an iphone.