This was one of the main issues that caused me to return mine, aside from the erratic WiFi and default app settings getting randomly changed randomly and every reboot.
SMS seemed to take a ridiculously long time to send. Sometimes up to a minute before it would actually send the SMS. It had to be the phone, because when I switched to the Ion and then to the Skyrocket the problem went away. Lots of times I'd be in a conversation and people would text me wondering if I had started ignoring them because the texts would take so long to send (and even after being sent, they still take a while to get to the recipient on any phone so you can only imagine the type of lag I was getting).
Doesn't seem to be a workaround for this issue, other than using another ROM on your phone which IMO is a huge hassle. HOpefully they push out an update to fix it for you guys.