It's easy to use these addon, as well as you can use concrete5.
All the addons presented in this website have passed the peer review.
Community Leader of concrete5.org
CEO of Rescuework, inc.
I use concrete5 as a base of the web service.
Nagoya Seminar Portal is a concrete5 based web service, linked with a mail magazine sending program. Users can post their seminar infos and the info will be sent to more than 6,000 readers.
Also, I make lots of addons for concrete5, and some of them are submitted to concrete5. This website is a sample demo site for my addon.