My oldest daughter attends the PA Cyber Charter School and loves it. Until 3rd grade, it is basically a supervised home school program where you act as the teacher. At the third grade level and beyond they can take cyber classes through a virtual classroom. They have a camera, headphone/microphone, and interact with the class as if they were in a traditional school (without passing notes or copying off of the guy at the next desk!)
As far as the level of education, my daughter is far ahead of others her grade level attending the local public school so I have no concerns there.
As far as socialization, you would need to seek out opportunites - the Cyber School has an organization called Family Link which sets up field trips statewide, roughly 1 time per month. I have my daughter enrolled in ballet, and gymnastics, take her to the local library for their 2 hour per week program geared to homeschoolers, and she attends Sunday School. She probably interacts with children on a social level more often than a typical kindergartner!
It's a little more effort, but I feel the quality of education is better and you know exactly what they are learning and how they are doing with it. You know their strengths and weaknesses and can more effectively teach them that way. Where will a child thrive more - with a loving parent giving them 1 on 1 attention or in a class of 30 kids with a single teacher? These are just my opinions but my 5 year old can read circles around others her age and can do math like a whiz and that is proof enough for me that this was the right decision for us.
Also, keep in mind that as the kids get older, you can have them participate in sports programs at their "home" district. If they want to do football, basketball, soccer, wrestling, etc., the public school district where you live must let them participate.
http://www.pacyber.org for more info.
Best of luck,
K.