It was announced last week that Wal-Mart is purchasing Vudu.  My experience with Vudu has been very positive.  I have not found any other pay-per-view service to have a higher quality video or audio experience.  They offer various quality levels with the top level HDX being near Blu-Ray quality in both audio and video.  This service is available with many devices including LG Blu-Ray players and stand alone boxes from Vudu.