I'm not sure if this thread is intended in the context of games or in the context of a phone.
I've had a chance to play with the Pre, the touchscreen interface is nice, but the slide out keyboard is crap. It's so small I doubt there's any greater accuracy than with an on screen keyboard, and I'd prefer T9 or SureType at that size. It's rather unfortunate, because with Facebook integration and the like it looks like a great phone (mobile communication and information device) and comes in a very comfortable size. I'd be waiting for a successor device, either with a better keyboard or no keyboard at all.
For gaming I don't think it'll have much to offer, I don't see any gaming hardware in there and the impression I get is that coding isn't that well suited to it.
The N900 I haven't been able to play with, but the keyboard simply based on being wide will be better (I've tried quite a few landscape slide out keyboards and I never had much problem with any of them), it also has the same integration as far as Facebook goes, and seems to go even further. Also, the fact that it runs a full distro of linux, which should make for some easy recompiling of apps means that the work to get a large software library for it will be smaller than developing for the device from scratch. All it will take is some people who want to port apps. I'm liking it as a phone much better than the Pre, however, Nokia reps have said it's step 4 in a 5 step plan for Maemo, meaning the N910 or whatever it's called will actually be designed as mass market, and Maemo 6 will support multi touch. If I had to buy a new phone right now, it'd likely be the N900, but as is I'll be waiting either way.
As far as gaming goes it looks really solid, it's got a 3D chip in it, that was demoed with bounce. Stylus + touch screen will make for some nice DS type games, and will probably work quite well for RTS and TBS games that already run on Linux. The slide out keyboard might be handy as well, although I suspect it won't be too great for emulation, it'd likely be no better than an iPhone as far as standard console emulation goes, but might be handy for emulating MSX, C64 and the like, and should be awesome for ScummVM. I don't think I'd get it just for its capabilities as a gaming device, but the controls look like they'll be better than the N95 8GB I'm currently on, which is close to being really nice but is also very limited in the specific games that work well. I also wouldn't be surprised to see something like N-Gage moved to Maemo.
Android phones look good in the phone aspect, I find they're pretty even with the Pre for the most part, down to the shitty camera, but more devices with a fairly unified interface means more development. I think the Dream is kinda ugly with the slide out keyboard, but the Magic appeals to me. On account of the shitty camera (like with WM phones), I think I'd probably stay away from it in favour of the N95, although the Xperia X3 is rumoured to run on Android, and the X2 suggests they'll be putting in their own good camera software. Landscape slide out keyboard + android + good camera should make for a sweet phone (and the X3 should be out around the same time as the N910 or whatever Nokia decides to call it).
For gaming, touch screen should be pretty solid, I figure the potential is about the same as the N900, right down to no multitouch. Yeah Android can be hacked to support it, but it's not in there by default, so a lot of games will likely work around no multitouch restriction. Enough of them come with slide out keyboards that there should be some decent suppor there too. However, I'm a bit worried that the handset design is so fractured that it'll end up being like S60v3 and N-Gage. A lot of S60v3 games assume a candybar phone, even though there are a bunch of sliders, so the games end up having much more shitty controls than they need to on handsets like the N81 and N95 (I'm particularly disappointed with NES and GB emulators that don't make use of the A/B button option on those two). Nokia might go ahead and do the same with Maemo, but right now it seems all Maemo devices have the same general physical design meaning there will be consistent game design as well, and it should be possible to buy whatever Maemo device you want with that design.