Sorry to say this did NOT pan out.  After controlled testing, I've determined it doesn't matter whether I use VST2 or VST3.
 

I've had the same slow-to-load issue in Windows 7 x64 SONAR Platinum (Dorchester) and Reaper 4.78. It's made me now want to avoid using the product. I see there might be an update, so I give that a try.

Cakewalk answer that they are working in a patch for this ...
In the meantime I have notice that in Reaper 4 if I click on the Vst Windows while waiting for the Vst to load the time is more faster. If I just ask for the Vst in the track and click Ok and wait, that could take minutes. If in the meantime I click to focus and activate the Fx window that load fast: from 7 seconds to 25 ...

Thanks for that Reaper tip mduque.

Hey'all - I'm glad to know it wasn't just my computer that I've been having troubles with. YES - I agree, Rap Pro loads very S..L...O....W

I preordered Rapture Pro, installed the most recent update and it still takes forever to load.  I guess it should have been named "Rapture Pro-crastinator.  I haven't been able to use it at all.  This is ridiculous.  15+minutes to load = Creativity Killer. 

Defrag your hard drive and disable your virus scanner? Same? If it takes 15 mins after that you should contact tech support not normal unless your library is massive.

My rapture pro takes over 10 minutes, to load up. this sounds so ridiculous to have to do all those re installs just to get it to work. Glads i only paid for an update  .I do like the sounds once  I get it loaded

Uninstalled DimPro and Rapture, reinstalled RapturePro. First load time 1-2 minutes, depending on what the system is doing. And I have really old computer. MS usual scanners are on. So, in case someone has to wait much longer and has "normal" 3.5 HDD (not notebook 2.5 disks, they are slow), something should be optimized.
 
At least I no longer have stable reproducible crashes at startup after the latest update. I have no idea why I was the only one with that problem, taking into account that was the only crashing program on my computer and I run usual Windows 8.1 64 bit.
 
 

There is some evidence based on a couple of observations (but not rigorous testing) that the slow behavior is not in loading but in displaying the UI.  I've seen this a couple of times (but I wasn't looking for it so my observations are a little indefinite).  When I have a Cubase project hosting R Pro but R Pro is not displayed, the instrument is already loaded but the UI isn't visible.  Upon clicking the "show synth" button on the track, I'm seeing ~80 second times for the UI to become visible.  This is about the same time when adding R Pro to the project in the first place.