Mine took about 10-15min to load and then to open in Sonar (Platinum) all the plugins, within 30 minutes I was recording. Possibly try a "Speed Test" just to verify your connection. As others have said check your modem, reset possibly uninstall/install.
 
Good luck and be patient!

Thank you all for the quick replies with your experiences.  It looks like it simply varies from time to time for whatever reason.
 
I ended up just canceling out after waiting another 3 to 4 hours for the install to hopefully complete but it was just stuck at around 41%.  I was nervous, but quit the install.  Restarted the computer all together.  Then I re-launched the command center and tried again.  I was pleasantly surprised to see that it started to download again around 41%.. then it scaled back to 40% and within about 7 minutes or so it was done.  The install process of the rest of the software, including the adding of Addicted Drums 2, plus the 3 added packs (thank you, Cakewalk for that) was also a painless process.
 
Because I was installing Sonar Platinum on top of Sonar X3 Producer, all my settings (midi, audio, etc, etc) and VST locations were instantly recognized.  So overall, I am pleased.
 
If I had to make a complaint, it would be this:  I had no options through the Command Center or through the XLN Audio install interface to choose where I would like the VST plugins to be installed.  I am very particular, and I was forced to have the .DLL files and other stuff installed on my C:/ drive.  That annoyed me because I have a separate physical drive where I have my VST effects and instruments all located.  I suppose I will live with it, just a few residing now on the C:/ drive.  Not sure how to go about relocating them, or if it's even worth it.

Thanks again everyone for chiming in and giving me the courage to quit and start again.  Whew!!

The gear in the upper right-hand corner of the Command Center opens the Settings page. The Settings page permits changing the install paths for plug-ins.

Thank you, Scook!
 
Ugh.. I wish I had seen that before I completed this install.  The OCD in me feels like uninstalling and starting over with the correct paths to the correct drive and directory for the VST paths... but, I think I shall live with it, frankly.
 
I still have to make an image of my OS before I can begin and continue on projects, and that's gonna take a while, so I think I'm about wrapped up soon.

You can manually move them after the fact. Just change the scan paths in preferences to reflect this and it should be fine.

Hi Noel,
 
When you say "scan paths" which preferences are you referring to?  Just want to be sure I don't go in a break something.  Thanks so much for your reply!!

the plugin and download location scan paths in CCC. Press the gear wheel in the top right hand corner.

Thanks Mike!  I will give this a try at some point soon and see if it works for me.
 
I'm wondering if aside from the .DLL files if there are any other files (larger sound bank files, etc) that I might be able to move off the C:/ drive like say, for Rapture and Dimension Pro which both got placed on the C:/ drive by default.  If not, then the .DLL files are all I need to move for now.
 
Thanks again, All!

Make sure you use a download manager or use Chrome which has one built in. Also, some ISPs might throttle you back if you're using too much bandwidth.

Noel Borthwick [Cakewalk]
You can manually move them after the fact. Just change the scan paths in preferences to reflect this and it should be fine.

Wasn't Noel talking about Preferences under Edit in SONAR, not CCC?