I did use Asda for a while but am back to grocery shopping in person. Mainly due to the fact that I wouldn't order my fresh meat or fresh veggies from Asda after a few unsatisfactory deliveries - veg on the bad side and stewing steak more fatty than I would have chosen if in person.
I don't tend to shop in Asda generally, preferring Sainsbury's and Tesco but last time I looked the S & T website was either too slow or I found it confusing to use or combination of both.
I found Asda's website a wee bit slow but I was happy with the actual working of it, apart from finding the cheap packs of 15 eggs, which for some reason I always struggled to find on their site.
It has been some years since I last tried Tesco or Sainsbury's site and it has probably improved since then.
I would go back to shopping for groceries online though, aside for fresh stuff.