I'm not sure what the Platform is doing when it refreshes the app list, but for whatever reason when I have Microsoft Security Essentials (MS antivirus) running, it seems to take a long time to load the list. However, I don't notice this problem with ASuite, which loads just as quickly whether MSSE is turned on or off.
My guess would be that the platform is loading info from all the .exe's in the PortableApps folder, which then causes the antivirus to have to scan them for viruses before releasing them to the Platform. So my question is, could the app list be cached somehow and only reload it when the Platform detects a change?