There is also one important mechanics issue to be familiar with. The fund's 30% short and 30% "extra" long positions will come in the form of swap agreements and forward contracts, which create counter-party risk. That adds an element of uncertainty, even though ProShares have proven itself more than capable in this area.
The ProShares Credit Suisse 130/30 fund falls under the realm of actively managed funds. Most ETFs are static, save for price fluctuations of the components. This makes using ETFs easy because you know what a fund owns now and what it will own in six months. That attribute has contributed to ETFs growing much faster than traditional mutual funds during this decade. But that's not the case with actively managed products. One byproduct of building portfolios with actively managed mutual funds is that, because of the lag in reporting holdings, investors often ended up being grossly overweight in sectors, such as tech in 2000 and financials in 2007. ETF transparency mitigates that issue, but investors still need to take time to look at their fund holdings periodically.
The importance of that issue, or the lack of regard for it, will determine whether actively managed ETFs ever gain traction.