I've been hosting one for a mate that lives in the US for a number of years, initially with the "classic" and lately with their freesat recorder.
Quality at the other end (I'm on Infinity) is excellent apparently and whilst not quite broadcast quality, he's more than happy.
I'd definitely recommend one, however will caveat that by saying that their support for older boxes isn't great - despite the freesat box still appearing to be a current product (http://www.echostar-europe.com/products/ConnectedDevices/Satellite/HDS600.aspx) their ipad and Android tablet apps don't support it and their phone app support is poor.
Having binned the windows programme that worked well with them in favour of a browser viewer that doesn't, I'd certainly suggest that if you do get one you seek out either the Pro-HD or one of the soon to be released boxes.
For those in different time zones, it's a real shame that the combined slingbox & pvr capability is no longer suppoted