Group meditation vs. Solo meditation Other than personal preference, are there known to be advantages or disadvantages to meditating in a group instead of alone?
Think about it - we go to refuge to the Buddha, Dharma, and the Sangha.  If community wasn't important, it wouldn't be one of the Three Jewels.  There's ample scriptural support for this as in Dhp 6.78, the concept of the kalyaṇa-mittata or spiritual friend, and the Upaddha Sutta where the Buddha called admirable companionship the "whole of the holy life".  While it can be difficult to find a group where you feel "at home", being around like minded individuals striving to the same end will only bolster your practice.  Furthermore, even those tiny annoyances like someone shifting during meditation, someone coughing, or a loud breather help strengthen your concentration and resolve.  Life is not perfectly collected samadhi!  We need to learn how to overcome obstacles.  What better time than when you're on the cushion!  I think it important to add that monasteries are supposed to be places most conducive to the spiritual life.  If solo meditation was somehow "better" than group meditation, then monks would not sit with each other.  Needless to say, this is clearly not the case.

I will also say that personally, I always sit more deeply when I meditate with others.  The ritual of driving to the same place, seeing the same people, and feeling the energy in the room - nothing can replace that!  

As off color as this metaphor is, I feel the need to share it.  One of my teachers once told me that meditation without community is like sex by yourself - it's pleasant and effective, sometimes something dramatic occurs, but always there is the sense that something is missing!  :-)