Currently I'm running IM+ on a Nokia 6790 Slide through Straight Talk.
The SMS chat function ends up causing me quite a few issues as, even though the message gets sent, my phone is constantly trying to send a text message. I've disabled the function but when I did, not only did it disable it on the chat client but it completely blocked me from getting any texts at all.
I've already tested this out quite a bit, when the chat client is up and running with SMS enabled I get their texts through the client but not normally(which really bugs me as I don't really care too much for the SMS chat function), when the client is turned off I receive text messages just fine, but the moment I disable the SMS chat I stop receiving all texts with the exceptions of ones from addresses and numbers not in my contacts. If they're in my contacts list though and I have SMS Chat disabled, I can't get any texts from them at all.
So the only option for me, if I want to keep IM+ running, is to use a feature I don't care for just so I can receive my texts.