there is a really nuts semi-natural rock garden in france, near morzine. it is a fireroad that has just fallen into disrepair. you come into flat out after a relatively smooth,steep fireroad and the rocks are pretty big and its stupidly scary - but i geuss thats what is fun. i find spd's make rock gardens easier becuase you can let the bike go loose and your feet stay stable which allow you to use your legs to lean the bike a bit easier.
I love rock gardens. They are what really seperate riders in ability, and if it is a rough line, you end up taking a different line almost every time(ie lower karpiel dogbone at northstar). Rock gardens are not just jump after jump and provide diversity on trails, with different/challenging terrain.