Within Ubuntu's software repository, you'll often find multiple packages for the same basic function, so you can try out a few different ones and stick with the one closest to what you need. For instance, after working a bit with Google Desktop Search for Linux, I decided to remove it and try something else. One of the other options for indexed search is a package called, simply, Search, based on the Beagle search engine project.
I didn't know that Beagle was a tad buggy, although I guess the revision number -- 0.2.16.3 -- should have been a hint. I installed Search, and soon noticed that whenever I attempted to search Ubuntu's help system, I got results that didn't match at all with my search terms. After some digging, I found that this is a known problem with Beagle -- or, rather, it's a problem with the way Beagle and the help system in Ubuntu talk to each other. It's also apparently a known issue (see here and here), so at least I wasn't alone in having been bitten by it. Removing Search and reinstalling the help system (which took all of five minutes) fixed the problem, so at least it was not that hard to back out.
Out of curiosity, I checked to see if there was an updated version of Beagle available directly from the project's Web site. There was, but there were no current binaries available for Ubuntu Feisty -- and if I have to compile a given item from source, that's a major strike against its usability.
What I'm worried about here is how a relative newcomer could install the Beagle Search package (something provided by Ubuntu's own software repository, which is why this is a little upsetting), not have much of a way to know about this issue, and then wonder what they did that broke the search function in help. That's a function they're likely to use a great deal; the more experienced users don't touch it as much and therefore might not see it as being a show-stopper.
Yes, I'm willing to accept blame for not doing as much homework as I might have -- but at the same time, I don't think it's asking too much for at least some warning that installing a package from Ubuntu's own software repository could cause something of that scope to break. Is it?