The first maps isnt that hard, just make some rounds and use your ghost against the Demo to see where you mess it up!
The last one (Complex String) is pretty hard until you get the hang of it. Mostly because there are SO many turns and you have to do them all pretty close to perfect to get a descent time ;-)
I read about the Panos too, thats what set me on getting gold in all the Time Trial/Attack maps. However it doesnt seem like you get the car in the Euro/PAL version, cause i DIDNT get anything after completing them all :-(
What i like about the Time Trial/Attack is that it makes you a better driver. you learn to handle the car without using "dirty tricks" such as using the rails or grass :-)
Also you need to complete the trials to get 100% (counts for 0.2%).
cheers
Anders