We chose DT Register because our client needed the Authorize.net gateway. But we're sticking with it - installing it on a second client site because of the support. The developers were fantastic at responding to e-mail inquiries - and even fixed and sent us new patched files to solve our particular issues!
If you need Authorize.net or PayPal for registration of events, DT Register is a great option.
We've demoed and used other registration components for Joomla, but for this particular client, DT Register was the perfect fit.