i bought a 24-105L lens from them back in November last year before reading any reviews, as I thought that they were UK based and looked a fairly decent outfit based on the quality of their website.
Shortly after I ordered I read a load of terrible reviews and got a little concerned, especially as they'd already charged my CC.
I dropped an e-mail to Vanessa at Simply Electronics saying that I needed the lens for an upcoming trip to India (which was true) and asked if she could speed my delivery up at all, as I didn't realise it would take up to 10 days to deliver when ordering.
She was very quick to reply and I kept a dialogue going with her during the following 2-3 days after my order - she gave me good updates and I received my lens 7 days after ordering.
I have to say that all in all I got a good service from them - I recommended a few improvements that I thought they could make to their automated updates re: orders and she said that they were already addressing them.
Would I order from them again - yes I would. I haven't yet and did consider buying my 7D from them last month, but in the end I bought from Kerso as I wanted a UK warranty for my camera. Price wise they were fairly similar.
I can also highly recommend Kerso, as many others on this forum & other forums do.