I'm pretty new at this, but so far the harder ones have been slightly better. I haven't hit any theme caches yet though. And I've yet to do a multi-cache.
I recently placed my first two caches. One is a really simple one, but it's an urban micro-cache which I kinda like the idea of. Hopefully cache-hunters will be stealthy enough that it won't be too short lived. The other is a 1/3.5 and involves a relatively strenuous hike of a mile or so (if you choose to take the short way and not do the longer 4 mile climb via mtn. bike), but the hiding spot is pretty obvious once you get there. This one is a bicycle themed cache and I hope the extra effort put into getting there will prompt people to put a bit more effort into keeping the cache-trinkets nice and in line with the theme. Right now it's got a small bottle of chain lube, a pair of tire levers, some new handlebar grips, some used bar ends, and a patch kit. Not fantastic stuff, but not exactly Happy Meal toys either. I don't plan on putting any more stuff into it except for some bike-related stickers that I forgot when I placed it. I'll need to upgrade the container before winter though...
At the very least I'll be able to keep a close eye on it 'cause I ride the trail it's near pretty regularly. If it turns into a box full of junk I'll probably upgrade the difficulty (Maybe make it a multi-cache.) and the contents and re-hide it someplace else.
-bikencacheguy