In my opinion, I think PSPgo is too small. Yes it is portable, supposed to be small, but there is a fine line between being small, and being playable. (I've thought the same thought toward iPhone) I am playing psp fat and even the distance of fat between left and right hand are already too close for long time playing.
I often get cramps if I play too seriously (button smashers, driving games, etc.). I cannot imagine being able to play on PSPgo for more than one hour. For casual gamers or puzzle gamers, it might be ok, but for intense and hardcore players, PSPgo is definitely "not" a go.
I am Asian, and I am not a big guy with big hands. I've often imagine the funny image of a big guy playing with PSPgo. His fingers are gonna be jammed together after a while. And that analog "stick" (I don't even think of it as stick) is even more of a joke. I am not a fanboy of fat psp or slim psp, but let's face it.
As cool looking as the PSPgo might seem, you gotta admit there is something seriously wrong with the design. I would be more accepting if the "sliding" part is horizontal rather then vertical. Com'on. It's not a phone, so stop trying to be like one.