I just rode my XC300 tonight for the first time with the EXP installed. I also have a WR250 Husky with a Rekluse Pro. I too thought I didn't need an auto clutch, because I know how to use my clutch. I'm also an upper level trials competitor.
But I have to say for woods racing, it's a definite advantage. Virtually never stall your bike. Don't have to worry about covering your clutch when brake sliding, going over obstacles, etc... And if you fall, the bike generally keeps running. It also helps hook up on dead engine starts and you bog-o-matic through the woods, if it's greasy and knarly.
I think it's great plus for racing. I know I get a 4" bigger trophy, because of it.
If I was just trail riding, I wouldn't bother. And wouldn't recommend one for a beginner either. Not that it won't make things easier for them, but you should know how to use the clutch, if you're gonna ride a motorcycle.