I switched to Kaiser at 20 weeks, and am so glad I did! When I called in to give them the name of the PCP I had decided on, I mentioned I was pregnant so they transferred me to the center near where I live and I was able to schedule an appointment with the OBGYN group right away. You can book appointments well in advance as well (I scheduled all of my appointments from 36 weeks to 42 weeks at my 36 week appointment). A lot of what they do is based online as well, so you can log onto their website and request an appointment, view test results, view the notes from the previous appointments, ask your doctor/nurse a question, view coverages under the policy, etc.
The group here mailed me a packet that I had to fill out and bring into the first appointment which was basic information about me and my health, and then I just signed a waiver to release my medical documents that they faxed to the previous OBGYN group. Very easy! They also gave me my choice of which hospital I wanted to delivery at during my first appointment.
The only thing to watch out for is double billing; I save all of my statements I get from them, and if they keep a charge on the next month's bill that I had paid on the previous month's bill, I just send copies of both bills and tell them that I have already paid such and such charge. They update their system and everything is good. To me it's such a small hassle from the problems I had with my previous insurer, and the quality of care I have received from Kaiser is so much better.
Good luck!