I've done B4B twice and had a great experience. Would definitely recommend it if you are intimidated by bumps, can't do them or just don't like them.
The purpose of the skiboards is to really dial in your fore-aft balance. With the limited length, you can't cheat at all and must have your weight over your feet at all times throughout the turn because if you're at all forward or back, you will fall over. It feels really unstable at first, but you get used to it pretty quickly. In my experience, the fore-aft balance stuck with me through the transition to normal skis. The course does recommend shorter skis for bumps (150's for most adult men), but you certainly don't have to go that short. I used 178's and 166's on the regular-ski days of my courses.
As far as the short-ski skills sticking with you on longer skis, the course gets a number of annual repeaters who use it to dial in their balance for the season. I had one of these guys in my group during a December session, and it was his eighth time through. I would probably do it annually if I had unlimited time and money. So at least some people find it really helpful.