Some places have been dirtier than I expected (nothing horrible though), some were much smaller than the pictures suggested, but the for the vast majority of cases it has been a good experience. When the experience wasn't good, I rated and commented accordingly, so the host got their rating lowered and maybe did something about it. I also met some of the owners, which was a nice experience.
For work I had to travel for 1, 2, 3 weeks at a time and it wouldn't have made sense in economic terms to get a hotel, so I'm glad airbnb existed.
New hosts might be an issue, but hosts with good reputation are, in my experience, not a problem.
I can see the problem where whole neighborhoods get used for airbnb, driving costs up for residents. I imagine that's a tiny minority of cities...where jt makes sense to enforce laws to avoid this. For the rest of the cities? In my opinion airbnb is a net benefit: if creates a product that didn't exist before and allows buyers and sellers to benefit from this transaction. For me at least (and the people I know which is, admittedly, a non random sample) it has been a good experience. I'm sure in most places it's riskier than hotels. Yes, there's a trade-off.