My main concern is that this will be hidden behind an option or an "extreme private" mode -- Tor seems too high-latency for the typical use-case of private browsing (image viewing and video streaming).
If you run a web service and would like to provide high-security anonymous access, consider running an Exit Enclave -- a Tor exit configured to exit only to your site. If Tor detects that your exit and your site share an IP address, it will automatically extend the normally 3-hop circuit to your node, and the traffic will exit the Tor network on your machine rather than an arbitrary node (which could be malicious).
I hope this finally kills the "only criminals use Tor" narrative the NSA and periodically, the media push. Everyone deserves strong anonymity.