The tax package to fund transit and roads in the greater Seattle area, known as Prop. 1, is a compromise: there are details for everyone to hate. I may be holding my nose, but I'm voting yes.
Consider what the measure does: it raises $10.8 billion to add light rail, HOV lanes, streetcars, park-and-rides and other transit infrastructure. It also generates $7 billion to fix some road choke points and complete several missing links in the region's network, for example connecting 509 and 167 to I-5. It's far from the sole solution, but it's a start.
For more info, take a look at this map.
What would be better? Funding much more transit, completing the projects much faster and explicitly including congestion pricing in the financing mix. In fact, the most persuasive argument against the measure is that any investment in roads lessens incentives for transit and worsens global warming.
But politics is reality. There's a huge backlog of infrastructure projects in the region and chipping away at it takes regional buy-in -- a process that in this case took five years. The dense areas of the region can't afford to pay for all the transit this area needs (remember the monorail?). To build support, there needs to be something for people who help pay but wouldn't directly benefit. Even with this package, congestion will still create a growing incentive to use transit; as alternatives start becoming available policies can be shifted to encourage even more use.
Assuming the measure passes, the next step should be reorganizing the governments that oversee the region's transportation to execute more efficiently. There will still be chances during the planning process to modifiy specific projects. These are all big challenges, not deal breakers.