Fans have compiled a list of the most common errors experienced on launch, some of which seem perfectly normal (long queue times after many server merges prior to launch) and some of which are not (server crashes from flying mounts). If you want to take a little time off from trying to get in and play, you can take a look at the recently posted glance at the creatures of Nagrand. Otherwise, there's not much to be done other than waiting for the latest round of hotfixes and hoping that corrects the major issues.
[Massively's sister site WoW Insider has published a detailed editorial explaining the launch issues and who bears responsibility for which ones. Managing Editor Adam Holisky argues that while Blizzard is responsible for the quest bottlenecks, broken terrain, server funneling, and griefing toys, it can't do much about DDoS attacks and their resulting latency and lag and queues, and therefore the studio should not be blamed for them.]