Some random thoughts as a coder: risk of overtime/crunch, unbalanced team (too many juniors/mids), poor processes, lack of flexitime/work from home, no seniors to learn from, company stability longer term, proper office chairs/PCs/equipment, unpredictable management/directors.
Yeah, it's tricky because startups can't solve all of those issues straight away, so they're not a dealbreaker for me, just something to factor in when negotiating.