I used to be a decent fan of P/E ratio for back of the envelope valuation yardsticks, but it seems more and more with the new economy there are business strategies to grow without profitability which effectively invalidates P/E as a yardstick since there is intentionally no "E". I sometimes look at Rev/Sales as a ratio but it seems too imprecise. meanwhile there businesses are more and more often set in a subscription model where you have churn factors, growth factors, and you have CAC factors. It seems like it requires a new back of the envelope yardstick but I don't have a simple enough mental model on it to implement yet. I wish I did.
Meanwhile I am still using a bare bones DCF model based on revenue, earnings, and income margin, but it still feels imperfect.
Stepner