I felt it to be a strong culture of comparison. Comparing job position, comparing employer, comparing income by implication. Ugh. Just not my ethos. I lived my 20s in that mindset and it's a zero sum game.
I also felt like it was so damn expensive to live there that even people making great salaries were constantly under pressure. To me, a pretty relaxed Midwesterner, it just seems like everyone is on edge.
The other thing that grated on me was the "funding equals success" mentality. So you got funded. Big. Effing. Deal. Go turn a profit.
It just isn't my kind of vibe. Like I said I'm a Midwesterner, the culture I grew up in is one of frugal living and understated successes.
My biggest problem with SV. It's like a rat race. It's all about doing the cool new thing.