I like that all of my domains are registered with this service, it is easy to use.
The interface isn't as user friendly as some other providers but you can learn how things work quickly enough once your using them daily - which we have! There's also an addon called Easy DNS Manager where if someone wants they can manage their own dns settings through our website. If there happens to be a downtime or error in one of these products then people won't really know until after its been out awhile since last time was great. We've never had any issues with registering multiple websites at same account so far.