Just like anything else you get what you pay for. I had a cheap jack stand flat out fail on me once. That was scary as hell.
I have two personal jacks. One is a 3 or 3 1/2 ton Torin. It weighs a ton but I like it because it is heavy duty. The other one I bought at Sams Club and is a 1 1/2 aluminum jack. I do an don't like this jack for several reasons. It's light and it is low profile, but on the other hand it's not uber duty but most of the time it works fine. And I bought this jack probably 6 or 7 years ago. The biggest downfall is however, the bolts have a bad habit of backing off!!! You gotta watch them (it looks like that's what happened to T1 3VOM's jack).
Yes most jacks can be rebuilt or if they aren't leaking much you can just add fluid.
I do like the jack that millhouse posted. My folks have an account. I think I'll have to get one...
If anyone has a Costco around them I strongly suggest checking out their Arcan 3.5 Ton jack. I picked up a membership specifically for the Jack...and it kicks some serious ass. Not only is it low profile (3.5") , but it has a pretty damn high lift height as well at 21 3/8". At only $99, you won't find anthing with the same specs anywhere near this price. Here are some pics stolen from another forum....
got the craftsmen jack for xmas, used it twice and its already seeping fluid. I hate to go out and buy a new one right now seeing how the in-laws just bought me this one. I have to drive the car up on boards to get it high enough to use the jack. I guess it will work for now, no more than i use one, but ill probably buy a low profile jack in the not so near future.