By becoming a member, you get access to the following:
1) 4-6 new articles every other month pertaining to all areas of pitching including mechanics, mechanics drills, strength and conditioning, strength and conditioning drills, nutrition, mental/emotional, coaching pitchers, etc.
2) Access to the old article archive.
3) Access to submit questions.
4) Access to the FAQ's.
5) Access to occasional video clips showing specific drills or exercises (downloadable to video IPODs).
6) Access to occasional recipes for nutritional snacks and drinks.
7) Discounts on videos, books, apparel (shirts, hats, pitcher's jackets), equipment (gear bags, mound rubber, weighted balls, elastic fitness cords, cold wraps for elbow, knees, shoulders), nutritional supplements, etc.
As to whether or not it's worth it, you'll have to decide that for yourself. I'd suggest that if you're interested purchasing some videos, books, apparel, etc., then it might be worth it to join just to get the discounts. You may end up paying about the same but you'll have access to the above stuff for a year. BTW, the website will show you both the member and non-member prices for the merchandise.