Extremely uneven, but when he's good he's pretty good
His best work, which I'd say is The Fast and the Furious, Dragonheart and Dragon: The Bruce Lee Story, is pretty good. Even his middle-of-the-road movies like xXx, Daylight and The Hurricane Heist aren't bad. But sometimes he turns in something like Stealth or The Mummy 3, which are both below-average efforts.
I definitely think we need director's like him though, guys who are able to make B-movie fun and who aren't trying to win Oscars. It's a shame that he doesn't work more often though, as he takes a while between projects. Hopefully his new film Speedhunters will be cool.