I've been using v0.3 for a long time now. I just installed v0.4 (and will grab v0.5 when it's available) and I noticed that after I installed it, enemies (NPC and Creature) seem to be more antsy. They won't stay still for more than a second or so, making it difficult to land long-range spells on them. Arrow shots wouldn't be an issue since I have a mod that makes arrow flight speed more realistic (faster) but spells are still slow-traveling and, even before enemies were hard to hit with spells because they would often randomly move out of the way at the last second. I haven't noticed this with friendly NPCs, but then, when I installed the new version of this mod I was around friendlies, and haven't been around them again since setting off for that Oblivion gate near Gweden Farm.
Also, to upgrade I just saved and exited the game, disabled the v0.3 OMOD, created the v0.4 OMOD from the .7z, and activated it. I have yet to delete the v0.3 OMOD.
I'm looking forward to v0.5, one way or another