RE Level II:
My 2 cents.
I personally am a swing trader, looking for anywhere from 2-4 % per trade, albeit I'll take more :^)
The value of level II to me is simple...once I have decided to make a trade and I'm ready to actually place the order, L2 can, and many times has, saved me money by simply watching the screen and noting the amt of orders at various levels.
If I see 50k buy shares from 9.95 to 9.99 and 5k sell shares from 10.00 to 10.02 I'm gonna wait until the price goes up to sell my shares. Supply and demand! (doesn't always work, but more often than not)
While I agree with the fellow who said you can't compete with the MM's, you can watch them manipulate the market and hopefully use what they are doing to your advantage.
Even an extra 5-10 dollars a trade adds up. Pays my commissions. Having said that I never use L2 to make a decision, only to time a buy or sell.
4God