I trust that Tether is, based on latest developments, not better than actually holding any coin or token. The risk of losing it all is given at any investment in Cryptocurrency. USDT was supposed to provide safe heaven the moment you wanted to go to bed. But it turns out that it incorporates the same risk.
It is all about convenience. If you were a trader and wanted to be 100% sure (if that is possible) you would have to go short on all investments, exchange those against BTC, LTC or BCH or ETH, transfer to an exchange like Coinbase and cash out in Euro or US Dollar. This process is extremely inconvenient and takes some time to perform.
For the time to come, I can see more exchanges offering FIAT trading pairs; this would not require USDT anymore from my perspective. BUT the exchanges would have to hold their reserves in FIAT then, which is incorporating other risks.