i have a revo and its awesome. everything is adjustable.
my reverse was working when i pulled it out but one of the pins in the gear snapped so i replaced the pin for the time being and yeh, just put the FOC in. havent looked back and maybe in the last dozen times iv run the truck reverse would of been nice to have twice maybe. only cuz i drove it into a tricky spot...
i put a locker in and liked it but not worth replacing drive shafts etc. so i put 100k diff oil back in the LSD and its good now. wanted to get 500k and still might but the shop i got my last order from had none.
first thing i suggest doing when u get one is remove the front left steering servo and put it in place of the throttle as its stronger and faster = better and if one fails for some reason you will have a backup to get you through the day at least. i personally have a steering servo ready to go in case either one fails. there cheap so i figured y not

also with only one steering servo which will do the same job as 2 it also stops them fighting and will increase battery life a bit.
spring mount exhaust is another thing i think they should of come factory with. they are more durable and dont SNAP instead they just pop out so u just have to pop it back on. easy for me cuz my truck loves being on the back wheels

40T spur gear is also handy
pull start is also a decent upgrade over the ez start. it starts much better with the glow igniter and pullstart
thats all i can think of for now.