Unnecessary, 5 searches a day for your own use is fine, and if you need to look people up, which I do sometimes upwards of 100 times a day, you can use TOPSHARK on pokerprolabs.
Tony Guerra was talking about it with the guys on Rounders Radio last night. His opinion was that sharkscope was not as good as PokerTracker or (the other name escapes me). Sharkscope almost falls into the data mining category which is expressly frowned upon by pokerstars.
Tony thought that the data provided by PokerTracker was best for improving your own game.
I'll go to Sharkscope to check out people when I'm not playing. It's almost always to see stats on someone I've never played before. IE, if someone is mouthy in the forums I want to see their stats.