Once the tunnel is up and running, we have not seen any problems.
Very fast service, above 10Mbps (Ingvars max encryption speed)
http://www.relakks.com

Known issues

Connection set up time

The initial handshaking times out if the servers are busy.
First setups should therefore be done on a non-busy day. Busy days are Fridays and Saturdays, avoid those.

On a non busy day, the tunnel should be ok within 15 minutes.(Usually within 5 minutes)
On a busy day, it can take hours for the handshake to get up and running.