I have the USM version of the MkII which came with my EOS50 back in the day. I find it to be a very sharp lens compared to some of the rubbish Canon is producing these days. OK, so it won't compete with an "L" series lens, but for kit, it's pretty darn good.
In the MkII Canon went for a lightweight design using composite plastics instead of metal which although works great, feels very flimsy in use. I am not keen at all on the focus ring being on the front element - easy to stick your grubby mits on the glass when you are trying to manual focus and it makes it look like a toy.
The MkI was much better constructed in my opinion but of course it weighs twice as much.