All mine bottom-shuffled, and never really crawled -- they could do crawling for getting over obstacles, but not as a main way of getting around.
Bum-shuffling has lots of advantages they can carry things, and can see where they're going better. Mine were all late to walk: dd1 18 months, ds 20 months, and dd2 is now nearly 12 months, and still won't take any weight on her legs if you lift her up, she just holds her legs out in front of her like a little plastic dolly.
IIRC there is a theory that crawling may be important for brain lateralisation -- the process whereby the left and right hemispheres of the brain become specialised for particular tasks. The reason, I believe, is that the coordination of opposite arms and legs required for crawling stimulates lateralisation.
My older two seem to be perfectly well coordinated, and were strongly right-handed from very early on, so the lack of crawling doesn't seem to have caused any problems.
Having said that, I do remember as a teenager having to help my goddaughter do fake 'crawling' exercises when she was a baby (she has Downs syndrome and the exercises were part of a programme her mum was following to help her development). She lay on her back, and we had to move opposite arms and legs to simulate crawling. But that may now be very dated, as it was in the mid-eighties. Having said that, she's now in her early twenties and at catering college and a has a serious clubbing habit, so she must be reasonably well co-ordinated.