Hmm. Not mad keen on wrap dresses - think they are (despite Trinny & Susannah!) difficult to wear. They need very good control underwear under them, else the tie can sit in any bits of fat and accentuate it (even if the wearer is slim). And I wouldn't wear it with boots as you have a gap between the boot and the hem, which can make legs/knees look fat.
I quite like the shape of it but not the pattern. And it depends on how tall you are too: M&S dresses often come at a very frumoy length if you are not tall. If you don't mind paying a bit more, the White Company have some beautiful jersey dresses.
I would wear something like that with boots providing it was short enough to see a bit of leg over the boot, so I disagree with Shandy on that point. Then again, I have quite slim knees and lower legs, so would want to show that bit! I think dresses (other than maxi) look really odd with long boots if the boot top is under the hem of the dress - it's a very 70s look.