I'm a perfectionist, so I'm still undecided about how I'm going to offer my design up. If the quality of the print varies significantly from the one I get from JKolton and one that's printed up at Kinko's, I probably won't offer my file up, just because I want my covers to look perfect. So, if the quality difference is great enough between the pro and Kinko's prints, I'll probably end up doing a run of covers, prewrapped on books.
That said Risu and WarMachine are still working on files themselves, so if you're not down for a run, they'll be able to take care of you.
I'm still just waiting for my print to come in though before I make my final decision either way.
-Nick