Although encumbrance updates when you enhance Strength, I keep having to go back to town early. My guy just finds 8 items (my base Str) and leaves. Even though he has 28 total Strength. Lame.
As a bug side-note, there doesn't seem to be any timer bar or text displaying whenever your character buys an item for the fourth equipment slot (mostly armor, right?). It's just instantaneously updated. The other items seem to be working just fine.