I've got KU19's on my car now, pretty happy with them. At first I wasn't so much but I think that was because they used some sort of grease or whatever to get the tyres on and got some on the tread and they were also over inflated. Now that's sorted they are good. I had Faulkens previously, they were fairly comparable, except the sidewalls on the Faulkens seemed a little stiffer. So probably prefered the Faulkens slightly but they were an extra $100 a corner.
The KU19 tread pattern is an obvious rip off of Pirelli P Zero's.
KU19's are supposed to be a little softer than KU31's which should mean they grip a bit better but wear a bit quicker. I had KU31's on a previous car, they were pretty good, Goodyear Eagle F1 GS-D3's were the best I had on that car but they were more costly and now some come out of China, which have a lower speed rating and they go for a fair few more dollars. Had KU31's on my current car but only while I was taking it very easy getting it over the pits etc.
I read up a bit on the LS1 forums and everyone who had them were happy with them. Seemed to be some people making assumptions on car forums that because they are relatively cheap they aren't good but from people who had actually had them, they all seemed satisfied.