Hello Daniel!
Hm... thanks for suggestion But....
we have the same ability to export products by Manufacturer.
In this case you should do the following (by steps)
1. Select "Show all grouped" drop-down menu from Product filter
2. Click on Manufacturer column and select Manufacturer Title
3. Select Export to .... ans choose the format. that's all you need to export products by selected manufacturer.
Watch small video example - http://screencast.com/t/tULpouQgQ
Screenshots -