UMD does not make a character more powerful by any means. About the best thing I've gotten out of it (considering that scroll DCs are PROHIBITIVELY high) is the use of Athus' Touch, which is another couple of healing spells (that don't work in a DMZ) and a bonus to Heal for bandages.Well, and Gloves of Harmony, but those don't do much for combat.
In my opinion, for a good economy you need a good spread of non-durable, non-droppable craftables across all types of crafts, focussed on low to mid level, which provide a definite advantage in adventuring in some manner.