Maybe this is just another of my, uhm...personal quirks..but I like dedicated (non-configurable) creepers and seats. Closest I come to really adjustable is the pneumatic up/down seat. Sorta like my generally negative view of most multi-tools (though those have saved my bacon a few times).
I`ve worn out a lot of creepers over the years. In all seriousness if you really want a creeper that fits you, is comfortable and is easy to use I`d recommend looking at the Bone Creepers. Seconding what Accumulator has said the pnuematic units are the way to go for a seat/stool. They allow you to get down to the rockers and up to reach the belt line. I believe in this instance 2 tools trumps the universal tool that attempts to do both.
Try TAKE10 or HELLO25 for $10 off or 25% off the Groupon deal. I always Google coupon codes before I buy anything on Groupon. It makes a good deal better.
The Sam`s club by me had one that looked like this one. I got the last one for 30.00$. They wanted 60.00$ I think. I like mine. Haven`t got much use, but, what little I used it, I like it