I've been lucky with apps. I have about 150, and don't have a crummy one in the bunch. I've deleted some just because I don't use them enough, but not because they're crummy.
Bummer about one app: It was a free one that worked perfectly for me -- a basic converter that did metrics and currencies. Then the developer improved it and loaded with many other options, which made it much more unwieldy for me, so I deleted it. The crazy thing is, I would've paid to keep it simple. Other people might find it useful with all the added functions, so I'm not going to bash it by name. I just wish there were the option to have kept the basic version.