I replaced the stock Kenda tires with the schwalbe marathon supremes in the same 32 width. They ride much faster, but still have all the advantages of the stock 32 width tires, and are also bullet proof. I put them on backwards, which I know doesn't matter, but my OCD is likely to have be swap them around so the "shooshes point the right way" sometime this week.

I just put ultegra clipless pedals on this weekend. The best upgrade for me so far has been the ergon grips. Much better on my wrists than the stock ones.