I did use Evolution for about a year (v1.0.5 ?) until it started crashing under load and became unusable. The only fix was to update to the version in unstable, but that required an upgrade of the entire Gnome kit'n'kaboodle. I dumped it at that point.
T-Bird has had issues with the index as a mail file grows large (>600 MB), but that seems to have been sorted. I've always been able to recover from this situation.