It took me 53 minutes. At my resort in under an hour. And this was on May 8, when DME was still an infant (it started May 5). My luggage took about 3.5 hours. But I didn't care how long it took my luggage, it didn't matter to me, it's not like I was waiting for it. I was off having fun when it "magically arrived" in my room. I packed our carry-ons with everything we needed for the first 24 hours (because airlines can delay luggage, you know). So knowing our luggage was going to be several hours, I packed our bathing suits, "beach shoes," change of clothes, PJs, toiletries, etc. The luggage could have come the next day and we would have been functioning just fine.
As for scheduling of buses, there is no scheduling, and also no set routes or set groupings of resorts. It's a dynamic situation, and buses are dispatched based on need. Because there are reservations, they know who is arriving when and going where, and arrange buses accordingly. This is done for maximum efficiency.
DME is great. Relax, enjoy it and enjoy WDW!
-- Eric