The CRJ's have a neat little "banana" on the MFD that shows you where you will be reaching the selected altitude, as well as a "snowflake" on the PFD where you would normally find a G/S indicator. They cannot be Autopilot-coupled.

The ERJ's have just a purple indicator (same as a G/S indicator, just purple) on the PFD. This cannot be Autopilot-coupled either.

They are for guidance only, and are dependent on the information saved in the box (ie VNAV G/S-angle). If you have garbage in, garbage comes out. Ahhh...the beauty of automation.