I hadn't noticed. Even though I've been using it more than I did when it had one fewer vowel in its name, I still think of it as a service that allows me to send inconsequential status updates to people using a mobile device (and not, for instance, a weblog platform or a dysfunctional chatline or a critical information dispersal mechanism); so if some of them don't go through it isn't really anything close to the end of the world.
To me, twitter is on the verge of uselessness in its current incarnation, not because of instability but because of the way that people are using it. I can't imagine having the updates of even the small list of people that I "follow" coming to my phone's sms mailbox anymore. The thought of having all of updates of all of the generally interesting people out there and all of the people who are "following" me that I should probably also be "following" out of social courtesy arriving by SMS is an altogether more crushing proposition. It already takes me multiple pages to catch up with my existing list via the web or the very nifty iphone application called twinkle; I'd think that the occasional meltdown would be a reminder of the new and fun world of things breaking to get better and a reprieve from information overload rather than cause for pitchforks and torches.