Hmm, regret is too strong a word, at least for my experiences (with the exception of Tassman 4, that's
a disappointment). There have been a few that were discontinued, so that was disappointing. But there were some I grew out of or that turned out to be less interesting than I thought they'd be. I can't remember them all, but the standouts are...Discontinued:
Grew Out of/Lost Interest
- Camel Audio Alchemy. I'm on Windows, not switching to Mac just for a Logic exclusive plugin, as highly as I thought of it -- that said, it was my first "big boy" synth, so there's some nostalgia attached there.
- Linplug Spectral. I didn't think highly of Linplug's other plugins...so I was surprised that Spectral is/was a legitimate masterpiece. It may be one of the finest soft synths ever developed -- and it was also legitimately unique. The only feature request I had for it was MSEGs. I'm still able to use it fortunately, but who knows which Windows update could be the last.
- Scanned Synth Pro. I was interested in this because it is one of the extremely small number of synths that have been developed implementing Scanned Synthesis, which is mostly unexplored and development is otherwise limited to Csound. SSP itself is rather basic and I personally don't feel it gets to very interesting territory -- plus, I think other synths just have better audio quality. Perhaps Enzyme by the same company may be better, but I haven't bothered to demo it. I'm curious to see if anyone ever develops an interesting scanned synthesis instrument.
- Aalto. It seemed to get quite a buzz from a number of people. I bought, tried it, made a bunch of patches, lived with the synth for about a year...but honestly, I thought it sounds like sh*t and still do. I really don't get where its loyal following comes from.
Otherwise, I've become extremely picky about synths and now own very few -- I guess a quality beats quantity sort of thing. The ones I own: Zebra 2.8/HZ, Serum, Diva, Spectral, Reaktor 6, plus orchestral and drum samples. I continue demoing new synths, but I haven't come across any that truly tempt me. Of the ones I own, Zebra gets the most use.