Jackson on Google AppEngine?
Looks like some brave folks are using Jackson on Google's App Engine (for JSON processing). Neat. Some minor problems exist (need to add a patch similar to one suggested), and chances are this is not the only thing one can encounter. But there shouldn't be anything fundamental difficult, based on succesful usage.
Oh, and on related note: Jackson 1.3 was just released. Check out feature list for details; list is long -- lots of fixes, incremental improvements -- but this time around there weren't many big features, just plenty of bug mop-up, added convenience methods, extended support for partially supported things and so on.
UPDATE, 06-Dec-2009: There have been some important fixes to issues runing on GAE and Android platforms -- make sure you use version 1.3.2 instead of 1.3.0 if running on either one (and please add comments if you do; whether it works, or you find other issues: sooner problems are reported, sooner they get fixed)