I'm only a very basic user but I like it a lot, search is very fast, very portable, you can create a customised open with dialogue (shortcut activated) for different filetypes. Constantly being updated.
You cant go wrong there - if you search for it here you'll find lots of people, advanced too, recommending it.
Of course it's dead easy to try it out - just download the portable version.
 I would say it's definitely better getting the lifetime license - it's updated so much that it's very worthwhile. I'm a fan of Dopus, but they just dont seem particularly interested when you come up with ideas for simple improvements - they *may* be included in the next version. With XY there's no guarantee your ideas will be taken on board but I've had positive experiences there on the XY forum [/edit]