The Joomla! Extensions Directory ™

This was the only product I found suitable for my site which has 25 different search engines, including hotels, yacht rental, scooter rental etc in various languages. So far I'm very impressed and will use it on other sites. I fully recommend this product and also paying for support to help on more.

Pros
For those (like me) with no experience of hotel booking systems, it removes a lot of the pain in setting up a complex application. They seem to have thought of everything and most of the modifications I wanted I was able to add with the help of a great support team.

It is flexible enough to be used with not just hotels but can be tailoured to fit any product that can be rented out on a daily basis.

It is reliable and secure and so far very responsive.

There are a huge ammount of plugins that really enhance the user experience.

Excellent support.

cons

It's quite complex but for the flexibility it has this is required. Any questions I had were covered in the forums or answered very quickly by the team. I fully recommend paying for support.

Level of support received
They respond very quickly and are unbelievably helpful. I have been loggining into the forums at various hours of the day and night and was happy to see Vince was logged in also.

They have helped me out of various binds instantly when they didn't have to as they were usually caused by me or other parts of my site. If not for them, I would have had a serious problem with a very impatient and demanding client after going live!!!

Ease of usage and deployment

Installation and basic setup (good enough for a small business) are easy if you read the instructions and use the forums. If you want to alter it design wise you will need some knowledge but there are templates available - I can't comment as I didn't use one.
It is a complex product and will take some time to get familiar with but once up and running you can find your way around easily. The important stuff which I had no experience of all was all prebuilt.