I'm pretty sure that you could also setup an OpenVPN server. It can be configured to listen over TCP port 443, so it can also get past proxies. It may be a bit more setup on the server-side, but it should be a lot easier on the clients.
In my experience, it is way more complicated on the server side and client support isn't that great either (no native iPhone/Android support last I checked). pptpd on the other hand is pretty easy to setup on server side and has excellent client support. The only drawback is that it is less secure than OpenVPN.
The PPTP encryption scheme is less secure, but the other problem is that it might be blocked at the firewall. If I remember my VPNs correctly, PPTP uses a different port and protocol (GRE), so it can easily be blocked by overly restrictive firewalls.
OpenVPN, on the other hand, can go through TCP 443, which is all but guaranteed to be unblocked.
But, you're right that there isn't any iPhone support for non-jailbroken phones. I'm not sure about Android, but I see less of a problem getting it working on an Android phone.
Single-user OpenVPN has become much simpler to set up than it used to be, because you can just use preshared keys and not worry about creating a certificate authority.
