Yes I'm having the same issues which I started noticing in the past couple of days. As far as I remember I didn't have the issue immediately after the latest OS upgrade. Besides, my wife, who is on O2 is having the same issues. I think it's a BB server issue, rather than a network or handset issue.
It is very annoying, particularly if you have grown to rely on the messenger as frequent form of communication. You may ask a contact a quick question, but the message gets stuck and doesn't get delivered until much later, by which time it is useless and actually causes confusion! Also, I noticed a disruption to the sequential messaging. So for example you'll write 3 lines of messages back to back. It won't deliver the 1st one, but deliver 2nd and 3rd and maybe deliver the 3rd one an hour later!
This is a major nuisance RIM, fix it quick!
