I have a V500 and V750, which are basically the same scanning units as the V600 and V800.
In my experience, the V500 is capable of results good enough for an 8x12 print, and the V750 is capable of results good enough for a 10x15 print. If I really work it, I can make an acceptable 12x18 print.
I also have a Nikon Coolscan V, and a 12x18 print from it is definitely better than a 12x18 print from the V750, but with a good negative and some work, the V750 print is good enough for most uses.
If you're gonna shoot, shoot, don't talk.