Thanks to Paul Kedrosky for a clear and useful analysis.
Levered ETFs, with the various targeted multipliers, reset their basis at the end of each trading day, which means that you are levered up only for that day.
This can have some remarkable and counter-intuitive results over a trend.
There is also a signficant amount of intraday slippage in volatile markets.
More Fun with Levered ETFs - Paul Kedrosky - Seeking Alph