We had a rough experience, but we'd use it again.
We did not use it for the way to SSR because we came in late the night before our check in and stayed offsite. But my Mom and stepdad flew in the day of check in so we arranged it for them. I used the webform to request the DME tags for them, everything arrived in the mail just fine. When we went to check in, we learned that everyone's contact info had bee wiped off the reservation with the exception of me. They blamed the new check in system for that. So I added everyone back to the reservation, mainly so my Mom when she arrived later that night could pick up her keys since we'd be gone. That went fine. But evidently this caused Magical express to have no idea on where to deliver the bags. Seems like since the luggage tags had their names on the bags, they could have figured it out. But they did not. So we got back from the parks late that night, where my Mom met us after checking in that night. No bags for my Mom. My mom called the front desk (at this point is was past midnight). They said they would call right back. She waited 1/2 hour and called again. They said they were still looking and would call right back. She called again and talked to someone else, who this time personally went out and saw the bags sitting wherever the bags were stored and said she'd have them within 5 minutes. So around 2am the bags showed up.
So the lesson there is to verify the contact info with DVC right before arriving. I know confirming a reservation is a good idea, but I did not bother since right before leaving we got the confirmation emails. Next time I'll call to confirm everyone's contact info if we are using DME again.