I assume you also have the Deore XT Shadow derailluer? This is an excellent component that is generally considered to be close in performance to the best Shimano offers, their XTR model. The XTR derailleur weighs less and is purported to be a bit more durable, esp in hard MTB riding. It also carries a premium price tag at about double the Deore XT.
After disassembling my Deore XT derailleur for a deep cleaning and the installation of the long cage arms I can attest to the quality of the build, from the ball bearings in the jockey wheels to the sealed adjustable clutch. I personally don't think it's worth the time and $ to upgrade this component. YRMV.