SMS and MMS Delays - A constant issue?

I am having lots of issues with SMS messages I send or received not being delivered to the destination or being received hours late. This is an ongoing issue with T-Mobile and now that I have the G1 I can confirm that this issue has occured on 3 different phones for me. This also occurs with MMS messages. I've noticed that it's a lot worse for messages being sent to another carrier, a short code, or email address. Typically I don't notice the problem when sending to other T-Mobile customers. Over the last year or two I've contacted T-Mobile about this and I've been given the run-around. I've also seen that if you do a Google search for "t-mobile sms delay" there are MANY people that are having the same issue.