I bought this myself after chatting with Carter and trying out the XT (hugely positive review is elsewhere in this forum). I have to say, I really like it. I have been using a G9x, fingertip, shell-less for the past year or two and have gotten very used to about 2200dpi, the almost flawless tracking of the mouse, and the light weight, but a) the spawn is even lighter than my older rev G9x. b) although at first i balked at the ring finger support, i got used to it within a week and find it to be extremely natural now in my typical fingertip position (but with a bit of extra support under my ring and middle fingers). i would say that the bigger issue though is that the tracking of the spawn is just significantly smoother and more natural feeling than the g9x. i would chalk this up to the lack of negative acceleration as compared to the g9x, but after quite a bit of staring at the two tracking mechanisms, pulling the g9x down to circuit board, and doing several other vaguely sciencey things, i think the avago sensor just feels better. i suspect it's because the laser gives significantly less information per dot to the processor on most surfaces (in fact, while my older g9x tracks on my white qck mass with some error, the g9x i just bought out of the last batch will not track at all on the white. literally, the pointer will not move).
so, if i had to find flaws with the spawn, and i do, if this is going to be a reasonable review, i would focus on two things:
1) i would like to see a slightly narrower 'more fingertippy' shell that increases the downward slope horizontal slope of the ring finger support and until it is maybe 10-15 degrees off of vertical, basically just a sculpted non-angular place to put your ring finger when holding the mouse fingertip style. second, i would narrow the top of the mouse, including the two main buttons and pull the heel in a bit. i would also get rid of the two left-side buttons. RTS players basically never use mouse buttons that aren't the big two. maybe call it the RTS version of the mouse or something like that and position it against the abyssus and mica.
2) i would go ahead and beef up the architecture to allow the same kind of interpolation between major resolution steps that the g9x has. some RTS users like 1600dpi, some 1800dpi, some 2000dpi, etc. they don't need the kind of 100% 1:1 flawless tracking that FPS users do, so a tiny bit of error is a non-issue if they can tune their resolution to enable hitting exactly the target resolution for the standardized sized UIs they have to use.