My experience of Waterstone's has generally been positive. I echo the comments of carpetmojo that the staff in their stores seem to know their stuff, and DO like reading themselves. Always a bonus when working in a bookshop! I was peeved to be sold a(n) (ex)display model PRS-350 though. They didn't say it was, but I guessed when looking in the bag on the way home - as the box had been taped up, instead of being fastened with the usual circular stickers. I knew once I opened it up that it was the same model I had been playing with. Not being familiar with eReaders at all I didn't realise at the time the zoom and options buttons didn't work. Once I realised I couldn't change fonts I took it to another branch and got a replacement - no questions asked.
The original store (Carmarthen) is a little smallish - two floors, and only really stocking bestsellers and the usual vampire/gothic/whatever fashionable teenage fiction. The second store I went to was Aberystwyth - a tiny single storey store. Both stores had Sony displays with Sony branding and the Touch and Pocket on show. In the former, both models were non-functional (batteries dead; or just dead).
I was disappointed with he first store as the young chap serving me was really enthusiastic and extremely helpful. No doubt he wasn't aware of the faults in the device I was sold, but I would have preferred he told me I was being sold an opened-box product. The staff at the other branch were lovely.