I like to move all my apps to the sdcard on my phone and leave as much internal memory free as possible. But the problem with the EVO3D is that it has a bug where when you reboot the phone, all icons associated with apps that are on the SDCard go to the little green and white android icon and lose the real icon. This is a pain, all the apps still work just harder to find them on your home screens. I found a workaround though and I hope that HTC will resolve this issue quickly.
To Resolve the issue go to Settings — Applications — running services — and now look for the HTC Sense service. Click that and then stop it. I know this sounds bad but it is not. The service will restart in a minute and when it does all your icons will be back. I know it is a pain but at least you can get them back. HTC needs to fix this bug though.
Hope that helps