50-60ms is OK, 100ms is starting to go a bit slow, 200ms is still usable, 300ms stales will climb some more
If you are in the EU you can just point your miners to eu. and it will auto-switch when that host is pointed back to the EU server
By the way, if you're connecting to the EU-server right now, you're actually connecting to the US-server. h2odyssee said so a couple of hours back. Try pinging eu.middlecoin.com. You'll find the same latency as with middlecoin.com.
What's a good latency?
I'm getting 240ms!
Doesn't seem too good.