David Prychitko tells of a wooden Marine Band Comb that swelled and spread after only a day of playing. It's definitely defective. Normal playing involves a certain amount of mouth moisture, and the wood should stand up to it. Get Hohner to replace it.
Some players (Mike Curtis, but others as well) claim they can't hear the difference between wood and other comb materials on a CD. I know I often can tell. Wood has a crisper, yet hollower, and slightly more colorful sound to me, while plastic tends to be mellower and metal brassier.
I had breakfast with Cham-ber Huang one morning at SPAH95, and mentioned that some players prefer the wood comb. He immediately volunteered the adjective "husky," which to me seemed quite fitting (by the way, I notice this in wood-combed chromatics, as well - I can hear it in the slight rasp Toots gets in his sound). I noted that he makes the wood-combed Bac-Pac harp (under $10) and later obtained some samples. I was quite impressed. The expected wood sound was there, and the response was snappy and full - much better than you'd expect from a harp in this price range. The timbre was brighter than a Marine Band - Cham-ber always goes for a bright sound - but the overall feel was comparable. For those who suffer from an unslaked Marine Band craving and can't afford a hit of primo Filisko, the Bac Pac may be a workable alternative.
By the way, Filisko, the king of the brass-combed harp, is now making harps with resin-impregnated wood combs (Richard Sleigh and David Flack are doing the same), giving a no-swell, no-warp, no-crack comb with all the warmth of wood and all the durability of plastic.