A new version of PreOs (version 1.0.3) is now avaliable. It fixes a bug on the AMS 3.10 for the TI-89 Titanium (SHIFT+OS wasn't working).
You can download it
http://omnimaga.earthforge.com/preos.zip.
UPDATE: Looks like T3 decided to keep me busy, yet another update (v.1.0.4)
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. This one fixes one bug with ReturnValue for all AMS and hardware.