I am still struggling with Shrew and my work's Cisco VPN. I get connected (tunnel established) and can even start my remote desktop to login and do a little work, and then I get dropped. I've tried 2.1.6 betas and now am using 2.2 alphas and getting the longest connection with 2.2, but its dropped every minute or so... very frustrating.
But, I am happy with using the "windows 7 mode" workaround. I installed the windows 7 mode and then installed the 32-bit cisco client (5.x) on the xp VM (which is 32 bit windows xp). I then saved a remote desktop connection shortcut to my server at work and made an IE shortcut pointing to my work's internal only webmail (why would they call it web mail if they keep it inside the firewall?).
To "publish" the shortcuts, you need to drag them to Settings > All Users > Start Menu > Programs and they will appear in native Windows 7 start menu. Works like a charm, other than the 5 second wait when starting the VPN connection for the first time.
I'll keep messing with Shrew, but I've made a spreadsheet and tried almost every combination of settings on the "Phase 2" tab and still no success.