I went to a UU church once.
From what I can gather, each church is different. The one I went to had a kind of a Christian church feel... not necessarily from what they said, but the format: the pews, a couple of songs that were hymn-like, a sermon, a choir, an organ.
But I heard that another UU church in my area has a more Buddhist feel to it.
I guess it's really one of those things where, since each one has its own unique "flavor," you should visit and see if it's something you like.