Leave management is the most valuable as they all started with leave management and then progressed to performance management. Of course, employee profiles are central to everything.
It is also very easy to use. Customers get on board with it very quickly. One of the selling points for BambooHR is that they have a very wide partner network. There are lots of other partners that have integrations with BambooHR. They have an open API. This is one of the things that is driving its growth because lots of people and companies are literally just building integrations of BambooHR to ride the wave. If you have an integration with BambooHR, you get sales. People are more likely to choose your product because they've already chosen BambooHR. That's how it is happening.
It is a cloud deployment, so there is only one version. They do the updates every month, and because of this, you are encouraged to send them feedback all the time. You never know. Your feature may be included in the next release.