[pheepster]

Clipless pedals are fine for most mountain biking, you just have to be comfortable using them (or twisting out of them).

If these shoes will strictly be used for your spinning class and those bikes have toe clips on the pedals, you might want to consider a road racing oriented shoe. They're generally a bit lighter, stiffer and transfer energy effectively, though they are a bit more awkward to walk in.

As far as brands, most companies make shoes with quality reflecting their price points. But like anything else, some companies fit differently than others so you'll just have to try some on. I like the ratchet adjustment on my Sidi shoes, but velcro straps are good too for allowing you to tighten the shoe without stopping. As stated above, they can stretch so being able to reach down and tighten them a little is nice.

Happy riding.