I have both a Matinee and a MA. The straps on the Matinee are definitely long enough to fit on the shoulder. I've even gotten it over a heavier coat. The straps on the MA will also fit on the shoulder but I find it awkward for two reasons: (1) I think the straps are a tad shorter, and (2) because the bag is a boxier shape than the Matinee, I find it an awkward fit on the shoulder. RM does sell longer straps, however, to attach to the MA and MAM bags. I plan on contacting them this week to order one (I was just waiting for the sample sale craziness to end!).
Lots of places carry RM bags and if you check the Deals & Steals thread, you'll find coupon codes for several sites (Label 360, Luna Boston, Active Endeavors, etc). If you register with Revolve Clothing you'll get an email for 30% off your first purchase, which you can use on a RM bag.
The last I heard, RM had a few sample sale bags left - I don't know if you can still order one, however. I guess they've had some problems and delays in shipping. It certainly wouldn't hurt to ask!
I've seen RM bags many times but was never interested until the Matinee bag came out. That was my first RM purchase. After I got that one, I went back & bought a MA bag which I ended up loving more than I thought! Now I want a mini to complete my set!