i know the best way to see the differences and the qualities is to play them, but since i may not have an easy access to them and am looking at the possibilty of buying via ebay or craigslist etc., any general comments?

Hi Jon & welcome to the club!
 
The main deciding factor for me would be whether or not you'd be switching guitars at gigs (w/out utilizing the effects loop, the furthur would be the less impeding when configuring your rig). A Series instrument would require a stereo or dual channel rig of some sort in order to make full use of its electronics.  
 
From a price standpoint, used Series guitars seem to offer more bang for the buck, while a used Furthur would hold its value in light of the fact that they are a newer model~ there are currently less of them out there, and the annual factory price increases make a used one or a stage model that much more desirable.  
 
Either way,  you can't go wrong. In a perfect world, I'd order a Furthur or neck-thru Skylark with Series electronics & a different wood recipe.

I don't think you could go wrong either way, but a Furthur just feels right to me. Series guitars have the possibility of being more idiosyncratic if you don't get to try it before you buy it. Both will sound amazing.

One thing is they sound damn good!

The strap obscures - is that an If you don't know Jorma, You don't know Jack shirt?
 
Peter

Good eyes, Peter. Sure is.
 
Bill, tgo

That is a really COOL guitar Bill!