I had an ebay turbo once, the dreadful 50 70 KKR Rip off (I was so so poor back in the day lol and shamefully it was on an R34). It was only Oil Cooled. You would turn the blade and it wouldn't continuely spin like a GTX3076R. You could tell the build quality wasn't the best. The only thing I did to it was put an orginal GT30 Wastegate on.
Funny enough the car wasn't terrible, I was able to "overtake" v8's, evos and rexs. 3500rpm at 12psi (LOL). Car was dyno'd at 230rwkw (Injectors Maxed Out). I used it for 20000km and took it off because I got cashed up. Turbo is still in tip top condition. But you get exactly what you pay for. I payed for old technology and I got sub-par performance. Compared to a GTX3076R their are huge differences.
For Street use yes it is ok since you'll only ever run for less then a minute. But for track unless you have a couple sitting around and are ready to replace. I wouldn't use them again.