While we use Ohanah for the front end listings (it's pretty and has a lot of nice auto features for listing events), we use DT Register for all the actual registrations.
For webcast registrations, we literally sell access to ACL groups, so when the user logs in, they can see the article they paid to access and it's got the live and on demand players embedded in it. I actually modified the form a bit so it's more clear that these require an account, and there's a nifty login popup button right on the form (putting one in the side bar confused people too much).
For regular events, we currently use single and group registrations, and I modded the form a bit for clarity. Overall it's been pretty slick!