I agree with the other post, if you've ever used a real backhoe, you'll be really disappointed with a 3 point hitch backhoe.  I can't comment about one on your skid steer, since I've never used one. 

I have a Deere backhoe, but needed to fix a tile blowout this spring when I was up at my father-in-law's.  He had his Long backhoe on a tractor, so rather than run 10 miles home and drive mine back, I decided to use his.  It did the job (other than I had to do a lot of extra shovel work) but I doubt I'll 'save' time by using his if it happens again.  If you're just going to dig an occasional hole not very deep, then it might be ok.  If you've never run a real backhoe yourself, then you might not miss it.

Mike