I have used AUT many times (now known as easybuyit, they have also branched out into ebay) when I first started using them they were quite new, and generally quite good and well priced.
However, now they have been around for a while, they seem a little less interested in the customer service side of things, and you never really know if you are going to visit on a good or bad day, it is often like dealing with someone who is bi-polar.
I have had days where I have walked in and within minutes bought and paid for items, but then again I have had my fair share of times that I have walked in and been left standing there looking at an empty desk, and no one ever comes out, even if there is a big queue. Its like they have gone into some sort of other dimension where there is no sense of time.
As I said they have been fairly good, but recently I can never seem to speak to anyone, and have on a few occasions waiting around only to walk out empty handed, and not seeing anyone.
Products wise, they have an ok selection. Prices aren't always amazing, and some of the products are very cheap and of low quality (laptop coolers, keyboards, recordable media) But you can get some really good quality products, I bought a flat screen monitor when they first came out, it still works to this day and I think I paid around £240 at the time!
So as I said, you can't really tell what to expect from them until you walk in there!