Oh yeah, I run a Conti Ultra Sport (no kevlar, just the regular) 700x28 on the back and an unknown 25 on the front (will replace it with the same 28 on the back when I need to).

I did a few upgrades to my Centurion, including a Brooks B-17 (had a black, now breaking in a copper/British racing green one), now running eggbeaters (will be moved to my fixie once built) and a new back wheelbuild (Mavic Open Sport rim laced onto the same hub/cassette as original).

I have DT shifters, which I don't intend to change but put in some Tektro cross levers so I can comfortably ride the tops/corners in traffic (and they work very well).

My frame is actually damaged (it was a free bike anyway) so I don't like to put much money into it directly, the wheel was the big deal - everything else I can move away - but I love the bike nonetheless, it's probably one of the best, if not the best bike I've ever owned to date.