I have a recumbant bike. I didn't use it for a long time because I was so into my Cathe tapes. But a few months back I had some lower back trouble and started to ride it again. (I know I shouldn't have done anything at all!). It made my legs and glutes sore.
However, I don't feel I can confidently make statements about how effective it otherwise was since I didn't isolate the effects of my bike from my diet or from other exercises I may have done. But rest assured that even as an advanced exerciser, it made me sore.
I've also had an upright bike and prefer the recumbant.
Jeanne