Quite honestly, you can play the game just fine on 64K ISDN. In fact, my brother and I, networking the connection, manage to play simultaneously when connected at 64K (We have a European account each). By which I mean pretty consistant <500 ms latency, which is perfectly fine for WoW.
We connect at 128K on weekends so that we can download stuff in the time we're not playing (such as overnight).
Our first bill was a bit of a shock, but only cos it included installation, 2 month's rental and the line was disconnecting and redialing when it was idle for the first 2 weeks of use (R200 wasted! We promptly sorted that out...)
But now that we're pretty dilligent about when/how we connect, and aren't having anymore disconnects/redials, I can fully expect my telkom bill to be around R450, which is perfectly reasonable. That excludes Storm's 128K connect15 ISDN, mind you, at another R125.
+-R600 pm for a perfect connection to World of Warcraft every night and all weekend? Yes please. I can't honestly say I'm a heavy downloader anyway, for the most part I'm only using my internet for the occasional download, university work, IRC and World of Warcraft. So I'm perfectly satisfied.