The standard way to search in iTunes is to use the search box top right. However, if you have a particularly popular or generic term, e.g. food, then you’ll want to drill down further and here’s where Power Search comes in.
Except it doesn’t on the place you’re most likely to search for apps, your iPhone itself.
So, if you really need to do some digging to find the app you’re looking for then you’re better off in iTunes and it’s back to Power Search.
If you’re looking for an app, then do your search, click on Power Search on the left and then use the dropdown to select apps. Then your can narrow your search down in several useful ways: by title/keywords, developer name and perhaps most useful by category and by device. There’s even the ability to search for free, for iPad and for Game Center compatible apps.
There are still some elements missing to make it really useful, such as searching by rating or by recently added. Recently added would be a useful element as often when an app has just launched it takes a while for it to surface in the search results which are geared towards the most popular apps. Fine if you know the app name, but if it’s that new cooking app from that magazine, then you need a little help.