calendar advice

[eluser]tim1965[/eluser]
Hi

I need to include a multi-user availability calendar into my website (with Mysql backend). For the sake of speed. I am thinking of going down the commercial route (i.e. buying one). I would use the CI version, but i thinl there would be a lot of effort involved in trying to get what i want, in the timeframe available to me. I had tried to integrate an open source calendar, but had a lot of issues with it as it made extensive use of $_GET. So my question is has anybody succesfully integrated a third party calendar product, if so which one, guesstimate of the effort involved, and pain level.
From the forums, there seems to have been some usage of easy PHP calendar in the past, but its not clear whether these were succesfully integrated.
Reaaly would appreciate peoples comments, and thanks in advance for any responses.