Every new MMO is going to launch with bugs, so why not soften the blow to the gamer with some positive re-enforcement. If game companies made their game's subscription half price for the first 1-3 months or so, I think gamers would be a lot less likely to get angry at finding bugs in their long awaited MMO. Instead of raging on forums (or blogs), I would be more inclined to say "thanks bug, you just saved me $10". The reduced subscription price would also serve to attract additional players to the game, who might have been on the fence about purchasing.
Games that don't have subscription fees (like Guild Wars), could use other incentives like half price in-game merchant costs, or double drop rates for the first month or so. It wouldn't have to be much, just as long as it counter balanced the negativity caused by bugs.
In the past I have held off buying MMO games on release, purely because I hate dealing with bugs. They make first impressions sour, and are one of the main causes of negative reviews. I think the smallest piece of positive re-enforcement (like reduced subscription fees) would go a long way toward aiding an MMO with a smooth release.