I'd try to do it this way...
What we are concerned about is that quite a number of those widget sites are of inferior quality
Try to avoid those by only submitting to good directories. Check them out carefully. Submit only to directories that don't accept all submissions, and which look like they might produce useful traffic. Traffic is why you're submitting... right?
Before your start suggesting us to make those links "no-follow", like everybody does in such cases, you should understand that those links are not exactly in our control and they appear without our participation in the process.
Worry only about the submissions you do control... and submit only to directories that look good enough that you'd consider linking to them. I'm not suggesting you do link to them, or that you swap links... and in fact quite the contrary... but you want to be that careful these days about what directories you contact.
Look for signs that the directory is well-selected, well-organized, and well-edited. Make your description as unique as you can (ie, different from your other listings), and leave it to the directory to edit further. In the present climate, I think I would submit these nofollowed links... and avoid anchor text in any listing you submit, just in case the directory is too eager to help you out. Don't assume that they're on top of Google's linking guidelines.
If the directory looks like a link farm, avoid it. Eg, if it has keyword stuffed titles, and/or lots of duplicate content (use Copyscape to check), the link probably won't do you any good, but it could hurt you. Again, look for signs of actual traffic.
Directories that list you without your submitting are out of your hands. I don't know whether Google is susceptible to many false positives or not... but, since it is out of your hands, just be careful whom you submit to. Keep good records.
Think of these listings as guest blogs, intended to drive traffic that might buy your widgets or link to you... not as direct links.
I don't know your market area. Do many of these download sites actually drive traffic? Can you spot the ones that will? That should guide you about which ones you approach.