IBM AIX Stability for XI (good and bad stories please)

We're running XI on AIX 5.3 (and hence the IBM JDK) and although I believe we've done all we can in terms of patches, maintenance and tuning across the board; we still continue to have downtime in the JAVA stack once a month.

Is anyone else running XI on the IBM JDK and how has the experience been in terms of stability.

Note - Also interested in the usage of your XI system (we have around 80 production interfaces).

Thanks,

Matt