I spent a number of hours yesterday downloading the 400 apps for the first time, but another program demanded an automatic restart of my PC during the install phase. This meant that the downloads that already exist in a previous temp folder are now "ignored" and the files have to be redownloaded thus wasting even more time.
How about setting up a named location %appdata%\temp\PA_Downloads\ which store any and all downloads until they are installed? That way if the process gets interrupted, it can easily be resumed without having to redownload the payloads again.
This feature is already planned.
You can see it in the PortableApps.com Platform Bug Report and Feature Tracker as "Ability to resume dropped downloads (may be in combination with setting specific location for download)".
You can find that post stickied at the top of the PortableApps.com Platform subforum.