It is hell though - recently setup this on a droplet, but getting all the settings right and diagnosed on Ubuntu and some Ubuntu and Android clients was complicated. It never seems to work the first time...
L2TP/IPsec is hell. OpenVPN is not more difficult to set up than a web server. Of course, you need L2TP if you want to use the built-in clients on Android, IPhone, Windows...
Yeah, mobile support was a bit tricky to set up for us as well, but we managed it with just OpenVPN. The OpenVPN app for iPhone at least was able to be configured without too much headache, although it only supports a subset of the OpenVPN options. It should be compatible with the config in the article.
For Android, there's an OpenVPN app too - it uses the very handy and neat Android VPN API and besides needing certificates in the right format (not the text versions), it works well.
True, that was my first try, and it failed miserably.
Back in the 2.3 days, Android had OpenVPN support (or maybe it was just a CyanogenMod feature). I wish that would come back.