It's ok. It's not the best and not the worst. It's is a decent program. But there are better anti-spyware programs available in my opinion for the same or lower price. If you really want to pay for an anti-spyware program SpySweeper is often on sale at stores like BestBuy and CompUSA for $20 for a year subscription. SpySweeper was free not too long ago at both stores as well. So you have to keep your eyes open for good deals. Most of X-Cleaners other functions (besides spyware detection) can be found in other free programs also. I would go with the tried and true free anti-spyware programs first, like Adaware, Spybot, MSAS, SpywareBlaster etc...and then if you feel you need it, add X-Cleaner. X-Cleaner would make an alright backup to your regular scanners/defenses.
I think its one of a so called "light and fast" spyware scanner and some history eraser. If you are in a hurry, this could be used quick. But, i could not just rely on this one scanner... i use this only as a back-up, that maybe they can detect something that my other scanners couldn't pick-up. I only uses the free version.
I also use the free version. It is quick (but doesn't have much of a database). I also use Bazooka. These are for in between full scans. BTW, X-Cleaner (XBlock) I believe was recently purchased by FaceTime Communications.