I did the whole series (Forum, Advanced, SELP). They are fantastic and life changing.
The Forum is a Zen Śūnyatā experience packaged up so that a westerner can get to the Śūnyatā moment without spending years doing Zen training. Its like being doing a parachute jump with an instructor. You can’t get there yourself but by the end of it, you know there is something there to get which is far more than I came in with. Most people never achieve radical honesty with themselves experiencing it is moving.
After the forum they throw in a free 10 week weekly seminar for reinforcement. This is so / so but it helps to make the Forum experience stick.
After that is the Advanced course which helps you achieve what you achieved in the Forum in other contexts. The Advanced course does pretty much what it claims to do, it teaches you to get Śūnyatā by yourself. In particular it helps you achieve breakthroughs in relationships. You now can do your own jumps.
They follow that with another more intense 10 week seminar called the SELP which teaches you how to apply the Forum to relationships and organizations.
Communications 1 I didn’t like very much.
All told I think the Landmark is a no brainer. If you are even considering it you should do it. Yes intermixing the hard sales stuff is very very annoying. But that’s what keeps the Forum so reasonably priced.