I am actually in the same boat as the OP, but my story has a little other twist to it.
1) I sold back a vintage synth to a dealer because I just didn't want this said synth anymore. I took store credit over cash because I "got more." I took a P12 (and some other gear) on trade because I thought the P12 looked pretty great (I had never played one yet at that point but was curious because I am a gearslut). I took her home and messed around with her. I think it is a FANTASTIC synth. The sound is good and the layout is PHENOMENAL. While there is some menu diving for modulation routing and other options, it is a breeze to navigate. SO intuitive.
I have spent a bit of time with her now. The presets scared me at first because I thought most of them sucked (as with most synths). So I threw down some Init Patches "or Basic Patches" down and started tweaking. I got some nice patches going, but nothing really JUMPED out at me sonically. Keep in mind that I haven't really used it with a lot of effects (other than on the unit itself) as I wanted to get a real good feel of its "raw" sound.
Lastly, when I work with synths, I like bare bones synths. I HATE menu diving and I don't really get too crazy with modulation routing. I have a modular for that which I get crazy with modulations. I love a simple straightforward synth. And for the most part, the P12 is laid out VERY simple with the ability to go very deep. I am just not BLOWN away by the sonic character.
2) Here's where the wrench gets thrown in. A couple of weeks ago, a friend approached me and said he met someone getting rid of their Studio Electronics Prophet 5 rackmount. I had been looking at these for a while but never pulled the trigger. Now, the offer was too good to pass up and I pulled the trigger on it. I haven't gotten it yet, but it is en route as we speak. My main reason was because a) I've always wanted to own a P5 and b) I really don't have room for another "Full" keyboard in my studio and c) I like Studio Electronics stuff. So how 'bout THAT. I get a Prophet 5 rackmount (Rev 3.3) and they drop the Prophet 6 yesterday. It's my fault. I should have waited until NAMM. I just didn't think Dave Smith was gonna introduce a new synth yet due to the P12, P8 and Pro-2.
So that's where I am at. I would love to hear all of your takes on it. But yes, I'm looking to get rid of my P12. It's on the classifieds here. I haven't brought it over to eBay yet but I might soon. It is MINT. I still have the box and plastic is on the display. In the meantime, I will still work with it a tiny bit just to make sure I didn't miss anything.
CHEERS!!! Lastly, I am VERY happy that the P6 was released for all those who have been waiting for an analog poly (like the P5) at an affordable price. The P8 is fantastic but I think this is what a lot of people have been waiting for.