Other than appliance vs PC, is there any particular advantage to open VPN versus using the PPTP server built into recent versions (<15yr) of windows?

Never mind. Answered my own question. Looks like there are some hoops to jump through to avoid vulnerabilities in MS-CHAP v2. However, if you VPN into something like a free-level Amazon EC2 server just for internet access from behind the great firewall... then I guess who really cares.