The staff here is always helpful and knowledgeable. It's not a huge store, so they don't always have exactly what I need, but I always head here before resigning myself to going to Home Depot.
I've also rented Uhauls and carpet cleaners there, and never had a problem with either.
Update: I have to change my review to 5 stars. I walked in tonight half an hour before closing with a vague notion of a silly project in mind, and one of the employees spent a good 15 minutes with me, helping figure out what I would need to complete it, and telling me how/where to get the bits that they didn't have in stock. I'm going to find what I need at Ace's website and just order it at the store.
I went to Home Depot the other night to look for the same items, and while a woman did finally ask if I needed help, when I told her what I wanted, she just said "our plumbing guys are out tonight so ... yeah".