Anyone had dealings with the cheaper internet camera stores??

I have noticed the internet camera stores like..procamerashop.co.uk, simplyelectronics, digitalrev, amazon..etc..  are much cheaper..

Has anyone had any dealings with them? I guess the majority of the stock will be grey imports but I was wondering if there is any risk and is it easy to replace items if problems occur?

Am thinking of spending a lot of money so obviously am a bit apprehensive!

Thanks...