Like others have mentioned, I've had no problems with my Harbor Freight 2.5 Ton Low Profile Floor Jack:
Did a leakdown test with no load for 24 hours without a problem, and worked just fine for quick lifts.
However, I did spend more time than I would have liked looking for fill valve for the hydraulic fluid (not included with the jack). Turns out there's a plate covering it with 2 screws on each side that need to be removed -- nowhere was this mentioned. Perhaps someone more familiar with jacks would have found this right away.
My only complaint is that the two piece handle is kind of wobbly, but for $70-$80 the jack is well worth this minor flaw.
And I wasn't able to use my 20% coupon, as it is stated in the fine print jacks are excluded from the coupon.