Can't say I have. Their website appears to be unprofessional and a bit sketchy.
After some quick Google research, I've noticed multiple people having problems with the phones they've purchased from them, such as not able to send/receive calls due to the phone being blocked.
I got a 4S from them last year (via their eBay store), advertised as B grade. It was in perfect condition as far as I could see, still using it and no problems. I would use them again.
Sorry to bump this up, found it in a Google search so thought other people might see it. They really are legit, my Mum bought a 4S from them in May and had no problems at all, great customer services, grade A, not a single scratch. I've just bought an iPhone 5 off them, should be here tomorrow. Would definitely buy from them again!
Yes they are legit, over the last year I've got:
iPhone 4 16GB
iPhone 5
and last month an iPad Mini.
The iPhone 4 developed a faulty home button out of warranty, was bought as a grade "A". The iPhone 5 was bought as a grade "B", arrived mint condition. The iPad Mini was the same, mint. I chalk the iPh4 up to it being in a case in a previous life so superficially fine but internally probably heavily used, I moved it on via gumtree. Prices are 'reasonable'.
More information on them is they also sell via eBay and they are basically the reseller for FoneBank.