Same with InterRegio - it can be very hit or miss
I can't say anything positive for IR.... Low quality old trains, mega dirty and normally delayed.
But i also use TKL quite often and have never had a real problem, the trains aren't the cleanest, but quite quiet, well heated in the winter, generally on time and nicely priced.
TKL from Głogów (about 50km above Wroclaw) through Wroclaw, onto Krakow somthing like 55zl cool :)