The Caltrain "Baby Bullet" trains will start running Monday June 7. The trains will make the San Francisco to San Jose run in 57 minutes (48 mile distance). The top speed will be limited to 79 mph, and the average running speed will be 50 mph. The trains will stop in Millbrae (BART to SFO), Hillsdale, Palo Alto and Mountain View (light rail cxn). Caltrain will operate 43 weekday trains in each direction between San Fran and San Jose. Also, "limited" express trains will operate hourly throughout the course of the day, skipping about 6 stops compared to regular trains.

Weekend service, which has been suspended for two years, will resume June 5 with hourly frequency. Construction projects have included installing passing tracks, new signaling, and track/station upgrades.
http://www.caltrain.com/news_2004_5_11_baby_bullet_weekend_service.html

Thanks for posting that. I last rode Caltrain in 2002, so I have not had a chance to see the improvements along the way.