VPN server recommendation

[Chavdar Videff <chavdar@mr-bricolage.bg>]

Hello List.

At our site we have to establish a secure VPN to a partner site in order to 
interconnect our subnetworks. On both sides we have Linux routers.

A fellow administrator suggested that we used OpenVPN.
The only VPN I have heard about is Poptop. 

Is OpenVPN a good choice? Are there better alternatives?

So far we played with gre tunnels (but no encryption).  Will it be enough to 
establish gre tunnels and try to force IPSEC through them?

All hints will be aprreciated.

Regards

Chavdar Videff