Top reasons to pull the trigger and upgrade from P08 to Rev2:
1. The 16-voices really makes a difference when stacking patches and playing any sort of strings, brass, pads or other patches with longer release times. I use stacks all the time, and for three different scenarios:
a. Classic bi-timbral (distinct sound on each layer) mixes.
b. Stereo binaural sound design where each layer is virtually identical, but hard panned L/R, sometimes with pan modulation... Similar to Poly Evolver type stereo fields.
c. Extended single layers via stack - Again, with virtually identical envelopes and filter sections, but now access to four core oscillators, plus two subs.. if you want to model Moog type of leads/basses with three oscillators, SE 4-osc stacks, or just other type of sounds where you have direct control of four oscillators and two subs.
2. The other major difference (for me) is the amount of mod slots. If doing more complex sound design stuff, having eight mod slots instead of four is huge. 95% of the patches I've designed use more than four mod slots... for dynamic performance modulation - like velocity response to various envelopes, pressure response to vibrato or filter characteristics, and I build in per-voice-modeling on virtually all patches - which really creates more of an organic feel of classic poly synth type sounds and analog acoustic ensembles.
3. And the built in effects are really nice to have too. There are some effects that I tend to run externally (notably delay, reverb), but I will often use built in effects as well. They sound great, and you can directly modulate parameters of them... I really like having them tied in with the patches, without requiring extensive MIDI programming for switching or modulation.
I definitely recommend the upgrade from P08 to Rev2. They're both very similar of course, but the Rev2 improvements are important ones, especially if doing more complex sound design, or using stacks for binaural stereo or other reasons. The only thing that might prevent me from upgrading right now is just waiting to see what the next release from SEQ is.