I received my Turbo Everdrive this weekend and wanted to post my first impressions. It works great with my Multimods.com region modded S-Video Duo-R, which is a relief as my NEO PCE card refused to work with it. It also works great with my TurboExpress as well. I haven't tried every game, but the couple dozen I tested out worked just fine on both Japanese and USA region hardware. I haven't tried any system cards as I have a Duo and a Arcade card already.
As for the power switch issue MottZilla is having, I haven't had a problem with this at all. I'm using a Kingston MicroSD card and the power switch guard clears the card just fine. I haven't had a lot of time to play with it as my 10 month old keeps me very busy these days, but I'll post some more impressions when I have the time. I will say this is light years better then the Neo PCE card which only held a finite number of games, and sometimes they would write to a bad block and didn't work. As a owner of the MD, GG, and Super Everdrives, the Turbo Everdrive is just as easy to use and has the same amazing build quality. I highly recommend it.