I draw my conclusion based on a combination of general market trend, market mood ,QQQQ, QLD, and QID, etc. It's pretty complex, but amazingly reliable. My QID/QLD trading account has grown amazingly well so far since it is set up.
QID and QLD are very good for swing trading if you can spot the market trend correctly.
For example, this year, so far, QID has two major up trends:
1. from 50.38 to 63.35
2. from 48.43 to 71.39
QLD has 1 major up trend:
from 19.46 to 32.68
But these QID/QLD are not for long term holding, just for swing player.
Another good thing is if you can spot the trend in QID/QLD very well, the trading capital can be scaled to 10M dollars and no problem at all since their daily trading amount to ~600M dollars.
I am still forward testing my QLD/QID strategies with real money now. So I can not say more....