I work in a learning technologies office and use Joomla for various help documentation and online staff professional development. We were in need of an online registration solution for our In-Service Professional Development sessions so I suggested that we schmooze the Extensions directory and add something to our Joomla site. Our PD sessions are no-charge and on-campus events so really, this extension was a bit too much for our current needs; on the other hand, DT Register is so flexible and robust that we decided to buy it so we can expand our offerings in the future.
More importantly, we believe that often, you not buying a product -- you are really paying for the technical support. Nathan and his team have been absolutely amazing to deal with and have answered every single, random question. Yes, they have even politely pointed out the obvious things I shouldn't of missed. :-)
I have yet to run into an installation problem or issue with the GUI that wasn't related to the end-user not reading the screen (yes, me -- skimming not reading). And have not been able to find any "glitches" in the extension. Finally, this is the only extension I have worked with that did not require extensive modification of the PHP or CSS files. Which, I believe deserves a pat on the back.
My only word of caution to those who may be "new" to Joomla and the extension world -- is to ensure that you spend plenty of time, before implementing the registration module live on production, reviewing each tab and the configurations etc. The extension is so robust, if you are like me and only need it for free events there are a lot of items to turn off.
The only change/revision I would suggest for this extension would be to change the default font colour for calendar view to black. Alternatively, it would be nice to give the end-user a choice on font colour. In our site, when you review the calendar from the front end, each event appears with a coloured background based on it's respective category. The font in the calendar is white. Because of this, the events are hard to read.
Overall well done on this extension!