(*Well, constant, except for the slow erosion over time as BTC are sold to pay the rather-steep 2% annual maintenance fee.)
Rather steep? I consider any fee above 0.1% for an ETF to be very high and I really don't understand that people buy these. With this ETF there is even an added fee for investing AND divesting.
Heck, if Secondmarket is holding the liability bag if coins from their ETF get stolen, I would be more confident holding BTC's in the form of their ETF in a brokerage account (once it becomes salable to the general public) than any online wallet service.
Don't be so sure about that. Take a look at page 12 (Security).