Hi Nick and Will!
So far my experience has been great. But as I've only been with them for a week now I will answer that question better in a few months time!
Within 2 days of signing up for the 21 day trial I had recieved my first game!
It comes in a prepaid envelope in which you post your game back to them so they can then send out the next available one on the list.
As there is only a limited number of half-decent games available on the Wii at the moment I opted for the entry level subscription at only £7.99 where I have one game at a time and can have two different games a month.
When a few more games come out I shall upgrade it to the package where I can have 2 games out a month and swap them an ulimited number of times, but until then I will stay with this package!
Apparently there is a referral scheme so if you decide to go with boomerang then PM me your name and email address, I will fill it in on the site and they will then send you an email with a link to sign up with etc.