Every time someone mentions Next on this site there will be people saying how vile and badly made it is but I honestly feel its like any large retailer of high street fashion - you have to sort the wheat from the chaff.
There are not many retailers where absolutely everything is vile and horrible including the children's stuff.
I never wear Next clothing myself - I ordered a Mac earlier last year and it was really bad and overpriced so I sent it back, but I wouldn't say all their collections are like that - I think that Mac was a particularly bad example. If I were to order a coat this spring I might find it very suitable - I just dont tend to look on Next for me.
I haven't really clothed my son in anything from there since he was a baby, but my daughter, however, 2nd child so less time to shop, and a chubby little thing so I found their sleepsuits etc fitted her shape well. Also, lots of tunic and legging combinations which for chubby toddlers is an excellent way to dress them, both comfortable, practical, but still sweet looking. Its not bad quality. It washes fine, doesn't fade, she grows out of it before it wears out. Some of the colours and patterns I dont like, so I dont buy, but there is a vast range, so you just avoid the stuff you dont buy. I've heard bad things about the clothing for older children, which may well be the case (I think they are guilty of the very grown up stuff for 9 year olds etc) but I haven't got to that stage yet.
And to be able to order something, assuming it is in stock, at 6pm and have it turn up the following morning is nothing short of remarkable - they are the only people who can do this. Amazon can guarantee some of their stuff before 1pm the next day but charge about £9 for the privilige and you have to wait in to sign for it. That's the only online retailer that even comes close in terms of speed. Most websites doing next day delivery need your order by midday or 1pm at the latest, which is still a very good service but they tend to charge for it ££££.
So, like most places, Next have their strengths and weaknesses, their pros and cons. But I've already answered the OP about the stock thing and I wholeheartedly agree, its very frustrating, and I think this Christmas was particularly bad - I think someone was ultra cautious when deciding how much stuff to preorder when they did Winter collections. Hope they learn from it, or I might have to find somewhere else when I decide my DD needs more stuff on a whim!