i've done it on all my planes and plan on doing it for everything in the future. it only takes a couple minutes and a little monokote, and like someone else mentioned, if you pick the colors and do the bottom of the surface it isn't visible anyway. (and remember there IS clear monokote...) it does improve the feel of the plane, more responsive...

it is benefitial to beginners! lots of beginners forget there is a left stick, and just peg it at full throttle and fly around. perfect conditions for flutter, which sealed surfaces can help prevent.