Honestly, many people play with pings around 300 with little or no effect. What matters more than anything else is dropped packets.
I played on a 50k connection through Savvis and averaged around 260-280. I'd see the occasional warp, assume it was my connection, land and reconnect. Just before HTC changed hosts my connection speed dropped to 28k. Savvis become totally unplayable with pings in the 600-800 range.
When they made the move to AT&T suddenly my 28k connection was averaging 230ms and zero packets lost and it's once more playable. I do occasionally see a warp and relog but it's much rarer these days then it was on 50k with Savvis.
So to make a long story short so long as you're not seeing alot of people warping or they're not complaining of you warping you're probably good to go.