I haven't gotten very far with my Juniper SRX implementation. I've managed to get a SRX210 (at my home) connected to an SRX650 using static routing.
I don't know what "Group VPN" is, I'll need to look that one up. We're just using the CLI and Web interface to manage the SRX routers/appliances.
I can post my "starting guide" on how I configured a Routed based VPN tunnel (as opposed to a Policy based VPN tunnel). I haven't done much yet but I don't have any spare 1010/1050s left to deploy so I'll need to start deploying the SRX210 pretty soon and then I'll need to start coming up with some configuration templates and best practices in terms of configuration and management. We will have two SRX650s connected to different ISPs so we plan to use OSPF routing (as we are with our Nortel VPN routers) to provide dynamic routing between our VPN branch offices and both our Internet links.
Cheers!