I set up a PS3 controller and it works great, but it will only work if I open up keygrabber first and then load mach 3. Is there something in mach 3 I need to configure so I don't have to open keygrabber every time?

You can change the target of your shortcut to open keygrabber and then have keygrabber  open your Mach profile.
Its been a long time since I did that and cant remember but will look to see if I can find the info.
Hood

Ok try this, seems to work here anyway.
Right click on your Mach shortcut and choose properties. In the target field enter this

C:\Mach3\KeyGrabber.exe /p MyProfile

The "MyProfile" will be the name of the profile you are using, for example if its the standard Mach3Mill profile the target would be

C:\Mach3\KeyGrabber.exe /p Mach3Mill

Also note that there is a space before and after the /p

Hood

Hey that works! 

Thanks!

Here's a video I made if anyone else is trying to do it.

http://www.youtube.com/watch?v=ChyLKj0ne1g