v1.4.4 of Google Maps for Mobile
Significantly more stable than recent prior versions -- hasn't yet crashed, and hasn't yet lost history data, but still loses bookmarks unpredictably, so it's still not fully stable. Worth the upgrade, and very useful even with the bookmark issue, but still a work in progress.
v1.1.0 of Google Mail for Mobile
Substantially more stable that v1.0.0 (which crashed frequently) -- hasn't yet crashed, and does an excellent job of handling email. Excellent application. Highly recommended.
v3.0.0 of Opera Mini
Significant update that retains look and feel of prior version. Wouldn't install if I preserved by existing bookmark data, so I had to start over -- may not be worth the update if you've got a lot of bookmarks. Excellent application. Highly recommended.