Well, a week ago (6 february) I finally made the 8868 truck from 1992. It's hard to describe how good this truck is. It's very difficult to make (all those pneumatic pipes have to be placed in the right way and there are a LOT of them).
This truck has a V6-engine which works with help of a rubber band, something I also don't see often. The 4 rear wheels make the engine run and this engine runs very quickly, like the first gear of box 8880/8448.
You can pump air in the pipes via a small pump connected to a 9V motor and this works brilliantly. It can be the new 8421 has the same feature, but if it's not, the 8868 is unique in this 'compressor & pneumatic' feature.
On the back of the truck there is a lifting arm and with the 4(!) switches you can do lots of things. One switch will turn the arm to the left or to the right (via 2 pneumatic cylinders), the second and thrirth switch will move the arm up or down (at 2 different places ofcourse) and the 4th switch will open or close the claw.
The 8880 is a very good car and probably the best 'non-9v-powered' technic set in my opinion, but this 8868 set is simply the best overall set at this moment (I still have to make the Space Shuttle (8480) which is even better according to many people). Btw, I like the 8479 truck, but it has less functions than the 8868 truck and although the whole bar code thing is cool, pneumatic powered by a 9v motor is even better than that. You can really hear that the motor and pump are working and that's not the case with the 8479 (ok, it creates truck-sounds, but if that is put off (which is possible), you don't hear anything at all)
The funny thing is that I never really was into trucks: "Cars were uber, trucks were not". This truck, together with the 8479 (bar code) truck completely changed my mind.
I don't have my own pictures of that truck right now, but I'll give a link to a site that can give you an impression of this car and why I'm talking so positive about it:
http://www.preussie.net/Lego/8868/index.html
When I've finished the space shuttle as well, I'll try to make some pictures with the digital camera which should be somewhere around here.