This is why I like them in this edition. A Belt of Magic Strength should make you Magically Strong, not provide a stackable strength increase. There is something much more satisfying about specific (non-stacking) effects. The Wizard makes himself a pair of magic gloves, and now he can wrestle ogres.
I do think they could be improved with ribbon abilities, like grappling or unarmed effects. Also, limited use or use-per-day items are cool, and would work well for strength, particularly for the non-strength user. I like the idea of a rogue who normally is average in strength, but has found a magic belt that lets him do something crazy every once in a while.