Hi I recently ordered online from Cartier. I live in the UK so not sure how different the experience is in the US.
I knew exactly what I wanted: a plain Love classic in rose gold. I had been researching this for a few months so my mind was pretty much made up. I printed their wrist sizer, got my measurement. Ordered on a Wednesday and the bangle turned up on Friday. It came in a large white box with "Cartier" printed on the underside of the lid, and within this box was the smaller red box, wrapped in the white paper with the wax seal. Also a buff coloured envelope with LOVE printed on the outside which held a small hard red folder with the certificate of authenticity inside. A red Cartier carrier bag with the silky red strings. Lastly, a small plain white envelope with a blank embossed card inside, in case you're giving it as a gift and want to write something. No travel pouch or cleaning solution, but that doesn't really bother me a great deal.
Pros for me is that I live a looong way from a Cartier store and unless I was after something exceptional, I can't be arsed to travel all that way. I work long hours, traveling to London and back is just something I don't want to be doing in my spare time. There's lots of good information on sites like this one which is satisfactory for me. I'm also pretty decisive, once I make up my mind I rarely second-guess my choices, and my feeling is that you can't go wrong with any Cartier piece (unless of course you get your size wrong) so how much of a mistake is it going to be?
As far as the in-store experience, I'm sure it's very nice but I can take it or leave it. Also there's a real danger (?!) of getting side-tracked by more beautiful things that sparkle suggestively in their polished glass cases... I can do without that (or should I say my wallet could do without that!)
So yeah, my "experience" was non-eventful and went perfectly smoothly and I love my Love!!! As I said, if I was looking for something more unusual and costly, I'd def make the effort to go see it in person. But for the pieces that are a little more ubiquitous I'd have no hesitation to order online again.