I have some major reservations about this fund as compared to Vanguard's who I think has the better business model and is well worth the higher minimums and slightly larger expense ratios.
My major issues with these two funds are that they are tracking an index Fidelity has chosen themselves, not one set up externally like most index funds. VTSAX uses the one from the Center for Research in Security Prices which I think is even better than a commercially driven index. Also, as people have alluded to, I believe Vanguard has a proprietary method for reducing capital gains distributions in their mutual funds by funneling the gains to the ETF of the same index since they are technically different classes of the same fund (like Investor vs Admiral class). Lastly, I just took a quick peak at the prospectus and as others have said they will be lending securities. What I found interesting though is that Fidelity's prospectus specifically listed Securities Lending Risk while Vanguard's did not. Are they going to be lending in a way that increases the risk relative to Vanguard's index fund?
That said, I only really use my Fidelity Brokerage for company stock programs and cash back from Fidelity's credit card which eventually I was hoping to replace. But I think I might take a stab at these funds when I get my next deposit, why not, they have 0% minimums which is awesome, especially for new investors.