Shaw -
Of everything I've looked at and listened to, the Prophet '08 is still my preference, and I don't see any reason for getting another instrument when my current one is doing exactly what I need. And yet, as I expand it, it does even more. So, my approach with the P'08 is to use one or two module versions controlled by one keyboard version. But I don't ever poly chain them together to increase the voice count. Eight voices is just enough for me. Rather, I MIDI them together, so as to create an immense stereo multi-timbral eight-voice instrument. I'm not into using many medium-sized instruments, but just two or three large-scale instruments. I realize this seems bizarre to some folks, bit it's what best serves my style of music.
The sounds I regularly use just couldn't be produced by a single Prophet '08, nor by any other synthesizer I'm aware of. Some folks complain that the P'08 is thin-sounding, but this only allows it to be multiplied without sounding overwhelmingly thick and clumsy. I don't think you could as effectively do this, for example, with a Memory Moog, whereas the P'08 is just perfect for this sort of layering.
That said, I probably will, sooner or later, add a VCO instrument - perhaps a Prophet 6 or a Moog if it seems certain it will provide a more raw analog character.