Just wanted to say that I got my RM Midi. It is a beautiful bag. This is my first experience with the pebbled leather and I really like how hardy it feels. I like to use my bags and not baby them, so it will be a good match for me. The downside is that the bag is heavy, probably more so because of the pebbled leather. However, it's a great size - fits more than I thought it would and is really a very useful size. I think I'm going to like it. I just took off the hangtags and some of the extra rings because I felt like I was hitting things with all of the metal hanging off the bag. It's amazing how heavy those little rings are!!
As for the shoulder wearing issue - I definitely agree with what everyone has said here. I can wear it on my shoulder no problem and it stays on their pretty well. I've even done it with a lighter fleece. I agree with those who said they probably couldn't do it with a heavy winter coat. But, I don't have any trouble flinging it on my shoulder and I've used the messenger strap to wear it cross-body. Works well!!
So, thanks for all of your help and advice!