I came across this topic while searching for problems with another large e-tailer (more of that in a moment).
I have used Pixmania for a number of years now and have never had any kind of problem with them. Delivery has usually been quick (with this, you're generally at the mercy of couriers, a few good, so many bad).
Now, of course there will always be problems, I've just been lucky so far. If there is a trade-off against the low prices these companies offer, service will always be it. So usually a local shop will do better in this area, because you're dealing a human being who may only have to deal with a few problems a day/week (and of course the face-to-face threats of physical violence are a great advantage .... only kidding

.
Now, I recently made a purchase from dabs which is my first one and oh dear, nothing but trouble. However, at this stage I'm guessing most of the trouble is with Parcelforce and GLS here in Ireland. However, it is very frustrating to get no reply to emails after days.
I did a search on dabs complaints today and I was shocked at the amount.
Personally, I feel I made an error by not checking out a company as thoroughly as I usually do.
The parcel eventually arrived (2 weeks, not 3 days!), just left on the doorstep, I hadn't even signed for it (now that is down to GLS entirely).
Well, two items were missing (SD cards, very small) and now I have the (I expect) painful experience of trying to get dabs to replace them.
Something tells me that I will give up (bearing the cost of these items) before it is resolved, but let's wait and see. I won't speak badly until I see no resolution forthcoming.
Then I'll probably order the same SD cards from Pixmania, as I'm pretty sure they'll arrive!