I've got an fc-16 go, had it for about two weeks. It's superb. I've been pleasantly surprised by the build quality, the screen is very nice and the snoac does a very good job (far more accurate than the emulation used by the genmobile and retrogen from what I've read). The battery life is indeed around 3-4 hours, if it was 6-8 I would be much happier. The design may look horrible, but once you actually get one in your hands it's fine. The form factor is comfortable and you get a nice adjustable viewing angle. It's comfortable to hold and I've not had any issues with the shoulder buttons mentioned in one or two reviews. I also find the d-pad is comfortable and responsive, but then I'm used to playstation controllers and I guess this is a matter of preference. Either way I think it'd be very simple to mod the d-pad if it bothered you.
One note for europeans and import game fans, the fc-16 go appears to bypass lockout chip issues, but runs games at 60hz ntsc. This means any pal games which perform a 50/60 check will not run (on a modded snes you can get past this by booting at 50, then switching to 60 once the game is up and running). Jap carts should be fine, however both pal and sfc carts won't physically fit in the slot unless you remove the cart location tabs on the unit (a very simple mod), just like the original usa snes!
Overall the console pretty much does what it sets out to do and does it well. If you want a handheld which can play real snes carts, I really recommend it. Until they release an improved model that is...