In 6.01B6, there's a new right click options to test the downloads. If you load an NZB, or search or headers into a post list you can right click "Test Download Files".
What this does is add the files to the download list and "test download" them so, you can judge whether they're worth downloading. What it does is attempt to download the headers for each data chunk and reports the results as a percentage of downloads that succeeded. You'll want to delete them and add them for real if you want them to download. I realize that the ability to change them into downloads is needed but, it's just not there yet.
The size column will show you the summary of the download results. It used fill servers the same way Newsbin would use them for the testing so, you can open up the compacted entry and see the colors of the servers that were used. If people want it I could probably add a "per server" summary of downloadabilty.