Hey Sven -
Loving GSA Email Spider, it's a great tool! I've been spending quite some time optimizing the tool with filters to dial in the tool to my needs.
I did have one feature request that I think would help, the ability to track statistics for projects based on emails harvested per minute or day based on the current scrape instance.
Kind of like GSA SER's VpM/LpM, I'd love to see statistics about how each scrape process is going. That way I can compare my projects effectiveness of scraping (based on current filters/options) to easily determine the best settings without having to write things down and check back in.