Like all Google services, Google Transit is currently in "beta" status. Unlike most other Google services, it really is beta quality: I've run into quite a few bugs, and the Tri-met trip planner gives faster/more accurate trips. But the user interface is truly excellent and intuitive. It will definitely become my default public transportation trip planner once they tweak it so the routes are as good (or better) than Tri-met's.

On a side note, the cost "savings" versus driving that they cite really irk me. I think it's very misleading. The basic costs of owning a car are sunk costs for me: My car is paid for and I have to pay the insurance no matter how much I drive. So the real cost is really just the gas and wear and tear, which comes to anywhere between $2-4 depending on how you calculate it. Taking Tri-met to work currently costs $3.60 roundtrip, and will be going up to somewhere between $3.80 and $4.00 next month. So I think if you already own a car, then public transportation is actually more expensive... of course, the real benefit is not having to deal with the time and hassle of heavy traffic.