Pretty good for the $$
Bought it last December to use as a mixer and headphone amp with my Kemper Profiler and an mp3 for woodshedding. Feature set is fine and worked good right out of the box, and the tone is clear with little noise, although a bit on the trebly side, After a year of using it 3 or 4 times a week, there is something going on with the phones jack, the left channel will cut out and I need to wiggle the 'phones plug to restore it. Couple other reasons it only got a 3.5: (1) there is no power switch and have to unplug it at the AC end to turn it off; and (2) the connector at the power inlet to the unit itself is not very god, it tends to loosen under the slightest motion and sets up an ungodly noise in my 'phones until I can get it back in. The power wires are very stiff (they seem to be solid, not stranded wire?!), as another reviewer had noted, so this happens more often than I would like.
In general, I like Behringer gear and for the price, it is very hard to beat the Xenyx 502. That being said, I have recently gone to using a Mackie 402LVZ4, which I had purchased for another use but which has been freed up, it has a power switch and a solid locking mini-XLR power connector (as well as much more flexible power wires), and it doesn't seem to have as much highs as the Behringer, and I have come to the conclusion that I should have bought the 402LVZ4 in the first place. But, like I said, the Xenyx 502 is really hard to beat for the price.