There are a lot of caveats but in general the "spend 2 days" thing is a lot less true now IMHO thanks to LLM's that can write mostly correct elisp from basic specifications. YMMV of course. I have found this can also open up to being a lot more than "maybe 5% more efficient" for niche applications. It's the closest environment I've used to where the friction between "I wish my editor could do <x>" and actually having the feature almost disappears.