A lot of people will give you strong opinions from personal experience, but UMD is often a wasted skill since you can already use wands of a lot of really important and useful spells.
Using arcane trigger devices is only scratching the surface of what a "chaladin" can do with UMD.
~ ~ ~
"That's a very interesting weapon you have there giving everybody the heebie-jeebies. Mind if I take a look at it?"
<feint><disarm><yoink!><UMD30 Emulate evil alignment to evade ickybadstuff>
"You don't mind if I hang onto this for awhile, do you? I'd hate to see anyone lose an eye."
<intimidate>