There are two items to be aware of if you are using TouchDown for Android on certain Android devices.  These issues have been reported, but do not occur in all instances.

1. When opening email messages, the viewer has been observed to cut out some of the email body and prevent scrolling.  This was observed on the following device:
                 -Verizon (HTC) Droid Incredible
A future release of the TouchDown for Android client will include adjustments to accommodate this issue.

2. Exchange contacts do not show up in the device's native address book application (People).  Using TouchDown's Copy To Phone option would normally populate contacts, synchronized through the ActiveSync Exchange component, to the device's built in address book database, but this is not the case with the following devices:  
                -Verizon (HTC) Droid Incredible
                -Verizon (Motorola) Droid X
                -Sprint (HTC) EVO 4G
With TouchDown v6.1.0007,  this issue has been resolved.  Contacts can now be synchronized to the device's native address book.