I drove an hour or so to pick mine up yesterday. Apparently in the US only the markets with active 3G got G1's. Luckily the store I went to yesterday was the only one to get any in my area. It was as easy as walking waiting three seconds and buying the phone outright. MY plan increased $10 with insurance and I've been messing with the phone for the last day or so.
UI is faster then most WM phones I've owned, but still not as responsive as the Iphone UI. Hoever I have not taken off the screen protector, I'm waiting for one from here -> https://www.zagg.com/
Hopefully the screen will become more responsive.
there is a slight learning curve. If you're like me and adept at figuring things out without a manual it shouldn't take more then ten minutes to figure things out. You just need to mess with it.
I still feel like it's not as "open" as the WM platform, mainly due to being such a new OS I don't have access to things like File explorer and the like.
The build quality was better on my JAM and TYTN II. My screen creaks when I press in the bottom right hand corner and the screen is much like the Diamond but I'm still a fan of the Iphone screen.
Otherwise this phone is much better then my TYTN II.
For phones: T-Mobile G1, HTC TYTN II, T-mobile Dash, I-Mate Jam, Mitac Mio 8390, Motorola A630, Nokia N-gage, Nokia N-gage QD, Motorola C331g.
For the car: Air suspension, ICE, I/H/E setup, more to come later. . .
For guns: ICS M4 CQB Pistol, KJW Sig Sauer P226, maybe a M14 EBR or G36K later. . .
Now only if I could afford modifying my car and my mobile phone addiction. . .ha ha ha. . . uh oh add airsoft to it too. lol