I have a large black patent Muse(my first YSL from 2007) and I love it. Such a classic that I still pull out and use frequently. It is a wonderful workhorse, timeless, classic, but still elegant and she holds her own wherever we are Good luck with your decision.
I can't think of any cons to the YSL muse. If you like structured bags, this is a classic. YSL leather is fabulous (especially the patent leather), I don't think you can go wrong with one.
I can't think of any cons either.. it's truly a lovely bag and a classic. I find the handles a little stiff and not so comfortable on the shoulder but it's really a "crook of arm" bag anyway so I didn't mind.
I just got my first Muse! But the box it came with is broken. I ordered at YSL.com. I sent them an e-mail but never got a reply. i like my bags in their boxes and bags.
I'm also new to ysl and I saw a majorelle for sale online but it comes with a shoulder strap. The majorelle isn't carried in stores anymore (at least I don't think) and everyone that has it in the reference thread doesn't have a shoulder strap. So does anyone know if it should come with this strap?