Can anyone give me the lowdown on how this works when you get a voucher alongside a purchased (physical) film?

Can you download onto a PC for offline viewing? Is the download then only viewable on that device?
Are specific devices registered? Is there a limit to how many? Can they be de-registered?

I guess my principal question is whether there is any downside to setting up an account and watching the UV film at my friend's house on their computer (as they don't have a blu-ray player). It is my film.

TIA
GetFrodo

Ps the voucher directs me to flixster, but wikipedia suggests that I could use any "portal" (for want of a better word). Is there any reason not to go with flixster? I have PCs, Android phones and iPads.

All the answers are here;

http://www.sonypictures.com/homevideo/ultraviolet/

AFAIK, flixster is currently the only UK portal for ultraviolet. Works fine though.

Not on all devices, peeps with Now TV and Roku boxes can't stream some of their ultraviolets.

I notice it doesn't support Chromecast in the UK. It does in the US though. Anyone any idea why?