Like already stated, Shyvana is a fast jungle.. But unlike other fast jungles, her ganks aren't that powerful (the only CC she offers is red buff).
However.... She is a great counterjungler. If you are against someone who either ganks a lot or clears slowly, all you have to do is wipe out your jungle, run into theirs, take it, return to your jungle, repeat. Most often Shyvana starts blue buff, but gets a "hard" leash so that she doesn't have to smite. Then she books it to the enemy jungle's red buff and waits in the bush to smite steal the red and then kill the enemy jungle.
Also, like said before again.... She is a good top. But even better than that.. Her W is a HUGE movespeed steroid, so she can counterjungle from top easily as well. If you're blue team, push lane, run back to river, then W to their red/doubles/wolves (depending on how your lane looks and where their mid/jungle is). If you're purple team, push lane, go to river, W to wolves/blue (depending on if enemy mid/jungle is getting the blue). Very nice top lane if your jungle is a counterjungler as well (means you aren't counterjungling alone, which means more success while doing so).