It has all the cool aspects for healthy mind, body, and spirit. You get: exercise, fun, views, health interesting friends, tinker points for custom mods, adrenaline, peace, fitness, travel...usually for free. What a deal. It's a groovy hobby.
Trail areas I've been to of note:
* Tahoe, CA: Mr. Toads Wild Ride, and The Flume
* Downieville, CA
* Aptos, CA
* Tam (Marin County), CA...all over that bad boy
* San Luis Obispo, CA: Montaña De Oro, Poly canyon