I wouldn't expect to see a full field thats based on a slippery surface, simply because of the safty factor involved.
Also a water field, also seems unfiesable because of:
-Time to setup
-Time to make the field water tight
-Amount of water needed
-Amount of space and labor needed
-Making a completely airtight robot would really heat up your motors and electronics
-electricty hazard.
-If your robot fails and sinks would it be difficult to retrieve?
Carpet is deffinatly the better choice, but they should go with different carpet types. I mean, who wouldn't want to run robots on Shag Carpet?
I would love to see something like 03's ramp agian.