I had an - unexplainable - lust for a Yamaha FS1R for ages... didn't make much sense (especially as I've gradually been moving across to a software only setup).
I just WANTED one.
Especially when I heard the fat, wide, metallic sounds you get from FM synthesis; much preferable - to my ears - to yet another subtractive synth. I held off, though - aware that it would be a waste of money, as I have not the time, patience or tiny fingers required to master such a beast. I continued to read up on FM synthesis, however... spending hours reading everything I could find on the topic.
Then, along came Pluggo 3 and it's 4 Op FM synth. At last I could have a fiddle about, and see how all the theory I had read applied to an instrument. I liked it. A lot - but it was tres limiting : no pitch envelopes, a limited repetoire of algorithms. I wanted more - but what ? The interface of FM7 left me cold (still does). So I tried FMHeaven.
Three words : "Mod. Wheel. Morph."
In conjunction with the programming matrix (which rocks, IMO - you tend to think about what you want the sound to do, rather than blindly flicking through algos), this is the business.
Sounds excellent, runs like a dream in Muzys and makes me grin from ear to ear. Like it.