An ETF to help ease of entry for more people (e.g. in retirement accounts, brokerages etc) will go a long way to helping people purchase bitcoin and take part in any future gains.
ETF's are great, but even if they are backed by the underlying asset, which the Vaneck & SolidX ETF is, people still don't own anything but a promise that for every share that they buy, a custodian has X number of coins in their reserve. It's fantastic for those looking to gain exposure to Bitcoin through a non hassle way, but I would always recommend people to buy and store Bitcoin themselves offline.
The third party risk is an obvious pitfall from a Bitcoiner's perspective. But we can also weigh that risk against the benefits -- namely, tax-deferred treatment of capital gains, held in a brokerage account covered by SIPC insurance. An ETF would be a huge improvement from the current ripoff Bitcoin IRA offerings.
Inevitably, people are going to want to hold bitcoins in their retirement accounts. The tax incentives are just too huge. From that perspective, it would be good to see better options on the market.