You'll be a better pilot for having done some.
Well I have done "Some" at Lasham and the Black Moutains, it is certainly different to powered flying by a long way. But, it is not in the same "type" of flying that the majority want, which is get in start up take off go where you want land and come back again with other pilots/friends/family, this is not an option for glider pilots.
It is IMHO purely "sport" flying and yes glider pilots who are experienced are probably some of the best handlers of wind/WX/thermals for staying aloft and physical handling ability, BUT it's not in the same league as powered flying, and I wouldn't go picking up gliding skills as a precursor to powered flying as you will if on a budget spend much needed cash and time probably getting rid of your different habits, and as been said not much benefit to logging SEP hours.