I haven't read this whole thread, but I will add my .02 anyway. I tried day-trading in '97 and I didn't like it much. Commissions were so high that you had to trade 1000 shares at a time to make money, and the MM's were worse than specialists. I traded for about 7 or 8 months, and lost about $500 on a 100k account. This did not include a few grand spent on ISDN (no broadband back then) and hardware.
Now, commissions are .01, and you can actually get executions at the prices you see. You might not be able to make money just by buying whatever is going up, but I made over $50,000 last year (my first full year of trading). I would have done better if I hadn't made a couple of real bad trades, but that is a lot better than a $500 loss. So, from my prespective, it's a lot better now than it was in '97.
I also don't do strict day-trading anymore. The only real reason for being flat every night for me was to limit risk. After seeing and experiencing worse moves during the day than overnight, I found other ways of limiting my risk. So now, a lot of my trades are day-trades, but I don't close them just because it is 4:00. So maybe I'm not qualified to talk about strict day-trading. Anyway, sorry for the ramble. Good luck.