Ohlone is a little like Mount Diablo in its climate (and therefore its flora and fauna) but the similarity stops there.
Ohlone is SO much more removed and remote. I see bald eagles every day, looking over my bowl of Cheerios in Kenai Alaska, but in the Bay Area, it is dang cool to see a bald eagle fly by. Waterfalls. Being miles from anyone. Hours, potentially days between seeing anyone else. It really is an amazing resource so close to such urbanized areas.
I was working in a backpacking store in the early 1980's, talking to many of the people who were instrumental in establishing the trail and I know a lot of people who took some of the very first (legal) trips through there. (I also knew people who did commando trips in that area before all the deals were hammered out with the Water District).
I've done it myself, much more recently and referred uber-outdoorsy Californians, Slovakian Forest Rangers, and others to it and no one has been disappointed.