I got a 256gb SSD for Xmas and installed it in one of the drive slots on my 2010 mini server running ML Client. The drive I got is a OCZ Vertex 4, which is sataIII, even though my mini only runs at sataII speeds. I figure down the road, when I buy a new mini, I can still use the drive and get the full speed benefits.
But even at sataII speeds, the mini is like a new computer.
Everything is much faster and the install wasn't really hard. You just have to be gentle with the little connectors. So anyways, now I have a much faster mini with a 256gb SSD and a 500gb hard drive and 8gb ram. I think it will serve me well.
I also ordered an enclosure for my now spare 500gb drive!