It seems that if everyone's ping stays below 200, hopefully below 150, there are no real issues. You might get the occasional hit that doesn't register, or maybe a small warp, but nothing terrible.
The Warpyness seems to get worse when an unusually high ping joins, or someones ping spikes. On the official server, I have never had a serious warp issue, but the cracked one.. you cram 32 people in there, and its like mechs are using teleporters.