It's got a killer interface. Handles local video extremely well. It used to have a decent ecosystem but Boxee seem to have pivoted away from that plan.
It never had the content providers - at least in the UK. We never got Lovefilm or Netflix. BBC iPlayer didn't work for months and 4od came and went then came back.
To woo the content providers that we never got Boxee shut off the hackability and killed a growing enthusiast and developer scene.
Movies constantly buffer for me with SMB. Over Boxee Media Manager it doesn't buffer, but does take longer to initially load.