Jon,
Since 3.1.2 just posted it has not been fully tested. Ideally a point version release from 3.1.1 to 3.1.2 shouldn’t cause any problems. However there was an Eclipse bug fix from 3.1.0 to 3.1.1 that did cause problems with XDoclet code completion. So there could indeed be hidden issues. However, I feel that it is worth a try. Mostly likely it will go very smoothly. Let us know if you run into any trouble and we will be glad to help.
Note: Remember to start eclipse at least once with the “-clean” argument to clear out your configuration/plugin cache.