This discussion seems to be mostly theoretical, so as someone who actually has $7 million, I'll provide my experience. In summary, not life-changing - my life is pretty much like the average engineer. I'm not spending like a rock star - your car, computer, stereo, clothes, etc are probably better than mine. (Although my house is a bit larger than average for Silicon Valley: 5br/3ba in an unfashionable city.) It's not enough money to feel even slightly important or rich in Silicon Valley. I don't feel like the "money problem" is solved; I plan to keep working for the foreseeable future.
I suppose I could move to somewhere like Kansas and retire, and live an upper-middle class life, but I don't see the point in that. (The "official" recommended spending rate of 4% would yield a high but not enormous income. Expecting 6-8% income is crazy talk.) The obvious HN answer is to start a company, but a) I'd be bad at it, b) I wouldn't enjoy it, c) I'd probably end up losing a pile of money, d) large opportunity cost, and e) health care.
Trying to summarize: the people who say a few million doesn't go far in Silicon Valley are right. It eliminates various problems (and I do sympathize with those with financial difficulties), but otherwise hasn't changed much for me. (Or maybe I'm just using it wrong.)