The main downside was that smaller companies kept going out of business (which is why I had so many jobs in that time period -- two of those companies disappeared entirely, one of them taking a month's worth of salary with it, which super-sucked).
A key thing, though, is that lots of really, really, really marginal developers got hired in the late '90s -- I worked with some of those at the first company that went out of business -- and they very possibly never got a job in the industry again. Crashes make companies a lot more selective, just as bubbles make them hire any warm body who can possibly even theoretically write code.