I'm unhappy about how limited the search functionality in SL is. You can search this forum for whatever you want with no problem. You can go to google.com and search the entire WWW. But in SL, you basically can't do that, and it takes a while to realize it. These are the things I think should be changed, and I believe doing this would benefit everyone:
1. For places and classifieds, you can only search for a single exact phrase. You cannot have multiple search terms. So if you search "clothes," this yields anything containing the string "clothes." But if you search "clothes+hair" as you would in a normal search engine, or "clothes hair" for that matter, this does not yield anything containing both the word "clothes" and the word "hair," but only ads that contain the exact phrase you entered, which is not many. So what you'd have to do if you wanted to find a place that sells clothes and hair is search for either term, and read each ad yourself (from a huge list, of course) to see if it also contains the other term. The limitation is very strange to someone that is accustomed to every other search functionality in existence.
2. Searching for groups is even worse. The only results you get are groups whose name starts with the phrase you entered. You can't search the group description. So if you search for "update", this doesn't yield "ETD Update Group" and so on, but only yields one group entitled "Update Lovers." So really the only way to find out about groups is through word of mouth.
3. The All search that lists the results alphabetically. I am guessing that like it did me, it takes many new players a while to bother realizing the tiny Classifieds and Places tabs, and so all the places and classifieds whose names start with spaces, exclamation points, numbers, and the letter A are shown to people who start searching in All while everything else is hidden. So if I had my way, either (1) the All tab would be eliminated and the Places tab made the default, or (2) the results from All would be separated by type and listed in the proper order.
4. There is no directory as far as I know. So you couldn't simply get a list of all "Shopping" places, but would have to be searching for a specific phrase amongst the places. There should be a way to list everything instead of only being able to get a list of ads containing a certain phrase.