Derek's solo works are wonderful. [ Moore and Rudess solo albums too ].
You have to listen to "On the Moon", "Day of the Dead", "God of War"....and if you hate Derek you will surely change your mind...
I've always liked this promo picture.
Also, cysquatch, don't diss Derek Sherinian. He was an extremely tasteful and stylistic keyboardist whose sound really meshed with Dream Theater during their middle era. For his time in the band, he did a good job.