I have been on one to spain (when I was at uni) cos they were so cheap last minute.
You dont always get named accomodation tho (i.e. they dont always tell you what hotel you will be in til you get there) so if you are a bit fussy about where you want to go its not always ideal - some of them are named tho so you can look up on the internet where you will be staying.
When I went it was fine, the hotel was nothing amazing but wasnt expecting it to be for the price - did me just fine, paperwork all cam thro in time etc .