I'm a mere music hobbyist, but have been at it for nearly a decade. I have limited time (usually at the expense of sleep) to "play" in my studio and I enjoy composition and playing my synths a bit more than I enjoy (what can be laborious) sampling, programming, and producing. So, the expansion boards are a dream for me - excellent sounds that fit well in a mix and that are fun to play and just satisfying to hear.

When I play/practice, it is usually classical music, so I love the Orchestral board. I "orchestrate" a piece how I want to hear it and go at it. The orchestral samples respond well to playing dynamics (velocity changes).

For composing pop music (as I do), the Session and Vintage Synth boards are my favorites.

I also own the Hip Hop and Vocal boards. I have the 60s/70s Keyboards board, but I'm going to sell it on eBay soon (look for it if you are interested!) because I don't have any room for it in my synth (I want to keep the Orchestral board I bought for practicing/playing and I've used the other boards too extensively in songs I've recorded for me to get rid of them).

Hope that helps anyone that might be interested.