I used VSAS for two of my away sub-i rotations. It worked beautifully.
When you decide on a program I strongly suggest you submit your VSAS application on the day the program starts accepting apps. Most programs will fill the early months with their own students, so if you want an early (ie, July, Aug, Sept) month you gotta be on the ball with submitting your app. Also, call each program prior to make sure you have everything in order, it never hurts to be a bit anal with this whole process.
I did a total of (3) sub-i rotations at the start of my 4th year and had my LOR's submitted by mid Oct. If your schedule allows, I suggest early sub-i rotations (July, Aug, Sept) vs. later (Oct, Nov) so you can get your LORs submitted and have your file completed before Nov 1st.
Regarding LOR's, try to get (2) from orthopaedic faculty, (1) from an orthopaedic chairman and a final one from a non-orthopaedic physician. Also, when you ask for LOR's try to not only give them your CV, PS, etc... but look into the programs you plan to apply and check to see if any supplemental forms need to be completed by letter writers. Two off hand are Univ of Wash and Yale.
On a side note, aside from titers, one of my sub-i away apps required a LOR from an orthopaedic faculty member.
Good luck!