I've used it with loads of different sound sources (drums, leads, whole mixes) and it does sound good enough for the price. It naturally can't compete with a 2000$ TL Audio units or such but neither does it sound horrible or amateurish and in most cases, it will beat the EQ of your mixing desk hands down, 4 bands of fully parametric EQ plus a valve control knob gives you practically free hands over the frequencies. Even better, each frequency band has a bypass function plus the low and the high bands can be switched between shelving and peaking filters, both features that other low cost parametric, like the TL Audio Ivory 5013, lack. What it maybe lacks in pure audio-quality bliss it replaces with features.
So how is the sound? Quite transparent, at least if you are not using the valve too much. For normal eq'ing, some boost and loads of cut can be used without too many artifacts and it is very accurate so you can pinpoint and eliminate many frequency-dependent problems easily. For creative eq'ing some other, classier units might be more usable since the unit distorts when loads of gain is used, especially in the low band. The valve control does help in this though, I've found that for sounds that need loads of bass boost it is often wise to boost the bass frequency you want and then turn the Warmth control almost all the way to the right. The bass becomes enhanced but the valve smoothens things up a great deal, producing a massive but still warm and usable bass sound.
When I got the unit the other valve wasn't operating correctly so I had to send it back. Now that it's repaired it's been working perfectly. I haven't had the unit for too long so I don't know how long it'll last, though.
All in all, a very nice unit for the price and a good buy if your mixing desk doesn't have a professional quality EQ and you don't want to spend a fortune on a parametric. Cheap, versatile, sounds reasonably good. Definately better than the EQ on my mixer or in my Yamaha A3000 sampler.