Came across this thread which seems to have generated a lot of comment and so I decided to sign up and have my say. I haven't bought from Portus but my colleague has and he is happy. There are a quite a lot of these grey market importers about and it is always pretty obvious by the price when they are grey. I have used these type of sites a few times - Simply Electronics - with good results 2 and a bad result another time - basically related to a lens I bought for my daughter for a holiday trip that was on back order forever. I cancelled the order then had to wait a month for a refund - not good but got the refund in the end. Bought that lens (sigma 17-70) from Wex in the end because of the timescales.
I also bought from UR Galaxy on Ebay years ago for a 70-200 non IS and was very happy so thought I would use them again when I bought my 300mm F2.8. This turned into a disaster and disputes and ebay police (just a term) involved etc. never did get the lens but did get a full refund and my name cleared. They were removed from Ebay not long after that - not sure if my experience was anything to to with that or if it was a combination of things.
Final and biggest punt was to get a 1DX from SLR hut. I ordered then afterwards read a load of bad press and reviews about them but interestingly, it was generally based on the "I wouldn't touch them with a barge pole" approach - with dodgy website, strange hours etc etc sited as the main reasons - in other words - no personal experience. I have to say I did lose sleep over it and even rang up to cancel my order but when they promised me a DHL number by day's end and an expedited order I agreed to hang on and sure enough 2 days later tracked by me at every point, it did turn up and works fine. The only thing was that it was set up in chinese but that
didnt take too long to figure out.
So at the end of all that - this is what I think.
If you want to do the morally right thing, buy from one of the reputable, uk sellers and have the peace of mind and no risk.
If you are prepared to take a chance and save potentially quite a lot of money, knowing the risks - these grey sellers do come and go - 1st Camera is one that springs to mind - then be sensible and at least get some payment protection and pay on a credit card. You might have to fight to get a refund or do a return or wait a long time for it turn up. You might have to go back to your credit card company and put the payment in dispute. You might have a very painful experience and as long as you understand the risks versus the reward then you are walking into it with open eyes.