802.11b pings around 3-4ms. This even holds true on a 5km link. If you go over two wireless hops, the ping will be around 6-8ms.
The real question though, is the backhaul. If it's leased line, you're looking at potential pings averageing 15ms - better than ADSL. If it's ADSL for backhaul (which it commonly is with the smaller WISPs), then likely around 30-40ms, maybe more, depending on load - probably still playable. However, if the backhaul is satellite, which is also shockingly common, the pings will be in the order of seconds; no chance of gaming at all.
I've played games here over wireless, connected back to my cable modem. On the wired network, I ping around 25ms in game, and wireless, around 30ms. There is no noticable difference in game, so which I use is a matter of convenience. So, draw your own conclusions from that.