I have 512Kbps DSL :Q, believe me, 768Kbps is not slow by any standard, unless you have to download 50Gigabytes of data everyday for some reason.
If you want slow...a friend asked me to help him clean the spyware on his PC yesterday. Since I didn't have my utilities CD with me I had to download everything from his computers (Adaware, MSantispyware, Avir, Spybot, etc). He has 56Kbps
It took almost 2 hours to download all that stuff. Now THAT'S slow.
Besides, most (if not all) online games use up just a tiny amount of bandwith. When playing WoW, for instance, It's always about 5KBps down and 2KBps up. It's all about Ping, and ping is not only about bandwith but also how far the server is from you counts. I get about 150ms in my WoW server (which a west coast server), but I'm in Mexico city, and the ping didn't change at all when I upgraded from 256 to 512.
I've also monitored X-Box live (which requires bandwith, can't be played with dial up). Again, the games I've tested (Halo 2 and SF2:Annyversary collection) barely go over the 6KBps mark.