I'd say, any download faster, than 100kb/s is good.
Believe me, I spent A LOT of time, tweaking my connection, playing with port forwarding, applying half-open connection patches, and yes, I saw on couple of occasion my download speed reaching 700kb/s, but normally, my speed would be somewhere between 100-400kb/s.
It all depends on number of seeders, and seeders to leechers ratio.
Upload speed is more consistent, because it depends MOSTLY on your connection speed, which depends on how busy your ISP servers are.