I've noticed a lot of people are using the fruit and nut cups as cupcake liners. Are these more difficult to remove sine they are more stiff?

Not at all when you take a look at Kimsmom's tutorial.

You actually bake the cupcake in a regular liner and then slip it into the nut cup.
So there are two liners.

Ok - here's the link!

http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1343861

I've baked directly in the nut cup and while it looks great, it is harder to open to eat. Cake didn't stick to cup but the rims are reinforced and much harder to tear.

When you find the nut cups that are approved for use in the oven (apparently the ones @ Michael's are now coated so you can't bake in them), I've read here that you simply cut a notch at the top edge of the rim, so that it can be torn and then unpleated/peeled with very little effort.