There are many reasons to use GVMax these include:
- Being able to get SMS/VM notification on your computer's desktop via GTalk (and being able to reply from the IM program)
- Sending group SMS messages
- HttpPost and general API access to GV.
- Auto responding to SMS
But I suspect most people use GVMax for the original reason it was built for, namely to be able to be notified of SMS/VM on the iPhone. Of those people I would say around 2/3rd of them use it via an IM client on the iPhone such as Beejive or Meebo. This is because until recently this was the most seemless way to integrate GV with a non-jailbroken iPhone.
Recently Apple has allowed a couple of Google Voice native applications into its AppStore. This is great news ofcourse. Unfortunately currently both of these applications do not provide push notifications. This can be fixed by using GVMax together with Prowl. GVMax monitors your GV account for SMS/VM and tells Prowl to notify the user. The cool thing about Prowl is that it is them able to redirect the notification straight into GVMobile+ or GV Connect.
So to these people I suggest that they switch to using the GVMax/Prowl configuration (see my previous posts on how to set that up).