Therm-A-Rest has recently released a new line of products called the Comfort System.  I recently have had the opportunity to test out two of the newest items: the Ventra Down Comforter and Fitted Sheet.  The Fitted Sheet has elastic bands which allows it to affix itself snugly to the thermarest pad.  You can even

You can even leave the fitted sheet on the pad when rolling it up, snapping it to itself so that it doesn't slide off when the pad is deflated:

If storing the sheet separately, it has its own stuff-sack:

The Ventra Down Comforter is very awesome.  It can be used just as a blanket in temperate climates, since sleeping inside of a down mummy bag can often times be too warm.  For extra warmth, the comforter has an elastic fitting which allows it to snugly fit around one end of the pad.  There are also several snaps along the sides which match up with those on the sheet.  This creates an almost sleeping bag feeling.

It seems to be a rather versatile system which packs up quite small - perfect for some impromptu truck camping.  You would probably not want to use this directly on the ground, but instead atop a ground tarp, bed of a truck, or inside a tent.  My initial impressions are that it is a good quality system.  I am a long-time owner of Therm-A-Rest pads (10+ years), so I can speak to the quality of their pads.  This looks to be a good sleeping system that integrates nicely with their pads.