It's definitly not cheating, it's an electronic aid. I use to use Expo all the time in 2wd electric racing on the throttle to eliminate wheel spin, but on 1/8th scales I never use Expo because there's practically an infinate amount of mechanical adjustments you can make to get the car comfortable for you to drive. Just my opinion, but I think it will make you a stronger driver and mechanic to figure out the car mechanically before you go to Expo
For example, on the throttle there is plenty of set up options in regard to the clutch that you can make, on the steering you can the change the ackerman to either have more or less steering response, but if your steering is twitchy at neutral it's probably a good idea to dial in a little negative expo (I think on my radio negative is used to "smooth" out the steering - check your manual