The studio that I work at has the XILS-lab PolyKB soft synth running on a number of different systems. All of them are Pro Tools HD based, but this will get used a lot in Logic as well. It definitely takes up a decent amount of processing power, but all of our systems are top notch so we don't ever have performance issues really. If you're going to be running this at home I'd recommend taking a look at the requirements to ensure that you'll be able to run it comfortably.
I really can't say enough about the amount of detail involved with the XILS-lab PolyKB. I haven't used original RSF PolyKobol analog synth that this is modeled after, but I don't have to do know that this is a great reproduction. It has sounds that could definitely be coming from an analog synth if I didn't know better, and an interface that matches up with the real deal. What more can you really ask for? I don't know what the price of this would be, but if you're in the market for a serious software synthesizer to use on an everyday basis kind of a thing, the XILS PolyKB is seriously worth considering. This thing is an absolute beast!