I am staying in San Francisco for four days. Has anyone taken the one day train excursion from San Francisco to Yosemite? Is it worth the trip? I want to experience as much of San Francisco that I can while I am there. Is this a good option as a side trip?

I don't know anything about the train excursion, but I have two comments:
1. If you know this will be your only chance ever to go to Yosemite, I could see considering this; it's not something you want to miss out on if you can't help it. But given that it's about four hours each way from SF, and is a place that deserves more time than a partial day, you'd probably be better off visiting another time, especially...
2. Since you want to experience as much of SF as possible and only have four days. There's so much to occupy you in SF and immediate surrounds for that mount of time, you might want to stick closer to town.

I did the bus/train trip last June. I only had a week in SF and could not afford the single supplement to do the 2day trip to Yosemite so I did it the cheap way. It was a long day - up at 6am and got back to my hotel at 11pm that night (there were problems with the rail line etc). Anyway despite these little problems I can thoroughly recommend the trip. Yosemite is breathtakingly beautiful. I was just in awe of the park. Make sure you take the trolley ride around the park to give yourself a really good view. It was a long day travelling to get there with only about two hours in the Park but very worthwhile. Do yourself a favour and go.

Anne in Australia

Dear Caitlin and Ann, Thanks for your replys on my posting. Your suggestions are very much appreciated

Jeanne,

I did this trip last summer via Greyline/Amtrak. I debated about doing it several years prior and was always sorry I didn't. After actually doing it last summer, I was so glad I did. I realize the majority of your one day is spent in route, but the train ride was a lot of fun. And after arriving in Yosemite the sights you see will more than make your day. I say go for it!

Sandi