The OSSolution team have thought of everything you could possibly want and more. There are oodles of advanced functionality, loads of Modules and smooth integrations. The translation functionality is excellent which lets you change all titles etc without touching a line of code. But if you do want to the PHP and style sheets are easy to modify to make it just perfect.
I spec'ed out a pretty large site for a customer that needed some very specific event booking requirements (training courses) and this extension had 95% of the functionality I required! The rest was a breeze to add with the help of the OSSolution team. Saved me months of development. They are not only super responsive but very very talented developers indeed. I'm starting to think there is nothing they can't do.
I completely recommend this extension and these guys. 5 Stars!!