If you go out today and rent space on a server, the provider will most likely give you a guarantee of 99.9% uptime, that is just 9 hours per year. At the very least a server just hosting a non-critical business application is considered reliable at 99.5% uptime. In comparison World of Warcraft has at least 4 hours of scheduled downtime per *week*, 8 hours when a patch is being applied. So already just counting the scheduled downtimes, WoW's reliability is only 97%. Now add the unscheduled downtime to that score, and the reliability drops to somewhere around 95%, which isn't very good by any standard.
I never even understood what Blizzard needs 4 hours of scheduled maintenance for. When was the last time you performed scheduled maintenance on your PC? What *happens* during scheduled maintenance? Can't be a backup, because the backup has to be done continuously, otherwise unscheduled outages would lead to up to one week of rollback, and that never happens. Are they reinstalling the server software from a slow Bittorrent server every week? Or does maintenance just take 5 minutes, but they only have 1 technician, and he does it one server at a time?
I'm certainly not one to cry for a refund, I don't want 50 cents per month refunded, no thank you. But I sure think that as MMORPG move more into the mainstream, the level of uptime has to be increased to be in line with other online applications. And World of Warcraft still has a long way to go until it reaches that point.