I've been thinking of upgrading my theanimaro.com forum to SMF 1.1 RC2.
* AJAX seems like a nice feature, letting people post/edit more efficiently.
* Searching within private messages would be nice. I have nearly 3000 private messages and increasing because I'm the site admin.
I'm also wondering if it has little annoyances fixed such as not telling the user the specific reason their avatar was rejected (too big, corrupted, GD wasn't installed with JPEG support, etc.).
But the SMF 1.1 RC2 announcement said it is still not to be considered stable software. We do not recommend its use in "live" situations, so I'm not sure if I should do this.
The final version of 1.1 will probably be out in not too long, a couple of months. If it were me, I'd wait until 1.1 goes final and then upgrade. The final version is the stable version and is meant to be used "live".
I have been using 1.1 RC2 for a while now and I really love it!