I ride a fixed road cycle with 700x23's around Boston - used to commute out to Watertown everyday for work -- the 23's worked well I think, I would upgrade to something a little bigger (28 maybe) but then I'd need new fenders... but anyway 23's are alright... they haven't busted yet or anything

Oh, anyway, I used to originally ride a Marin Muirwoods until was stolen, then for a while I rode a somewhat modified Raliegh hybird city bike thing... i like the road frame and tires MUCH better...

For strictly city use (not commuting long long distances) I also enjoy the Kronan army bike... which has BIG tires and upright sitting, quite comfortable for those trips grocery shopping or doing laundry (its so sturdy... I can fit my entire wardrobe on the back rack)