I bought one in 2003, when they first came out. I took him back in 2004 and he seemed to be working just fine. Being slightly over obsessed and with more money than sense I did buy the new one too this last trip. I will take him along in November I expect.
If you have got as far as the end of Main Street and he hasn't buzzed, he might need re-activating. There are a couple of points going down Main Street that should set him off. To re-activate try on Main Street in MK, the shop Main Street Cinema (on the right as you are walking towards the castle) was where I got my Pal Mickey (number 2!!) and they had all the gizmos needed to activate him. Hope that helps.