I recently moved to the VC side from software engineering. I was sure that the biggest value that I'd have for startups would be my engineering experience, but what founders seem to appreciate most is direct feedback. Even when saying 'no', I try to add some useful bullet points about what my fund's concerns are, what we'd like to see in order to invest in a latter round, any oddities that I noticed on the website or mobile app, etc. Founders seem to really like that -- especially product feedback.