The small size also worried me a lot before i touched it. For example I hate the shape of the g9, that feels just wrong and too small.
But the shape of the spawn is way better imo, it's pretty wide which I think makes it comfortable to use, while it is still short.
As I said I think i have medium sized hands and have no problems at all touching this mouse; it fits perfectly when I claw-grip it.
For longer fingers and fingertipping I think it'll work fine.
And I didnt like the g400's shape, because I found it to be too long to claw-/fingertip-grip it.
I didn't feel any problems at 800 dpi, though I usually use it at higher dpi. I even leave it at 3500 dpi now and turned windows sens down to 4, so on the desktop it feels like 1750 dpi, which is a likely speed. I have it screwed up to 3200 dpi for gaming, where I use a very low in-game sensitivity, so it results in real mid-sense.
So, if you think 800 is problematic or unstable you can still use the higher dpi levels and tune the sensitivity softwareside.
I think the spawn's scrollwheel is a tad harder to press, but not that much that I remember especially. But the extra buttons under the scroll wheel have a so much better feeling than the buttons over and under the g400's scrollwheel. They feel really wobbly, dont they?
I found it impossible to keep my ringfinger in this position, though the mouse is probably made to be held like that. My finger always slipped down to the side, where it pushed on that lip and gave me pain.
Regards