I'm contemplating a new camera next year and am seriously considering the QSI 583 too. Looks like a full package at a very attractive price.
I'll be using it on an f/5 Newtonian, so I hope it doesn't vignette but it seems people don't have problems with that.
Only drawback I can see is the somewhat lesser cooling ability, but with me being in NZ that won't be a problem for most of the year
