Have you tried the newly-ported GNOME Web browser, mentioned in the release notes? It seems that it solves the "web browser problem" many users have complained about.
The lack of a built-in solution for full-disk encryption is also a blocker for me. It's something I keep meaning to try and tackle (say, by porting over OpenBSD's FDE implementation), but I ain't quite comfortable enough yet with Haiku's codebase to even know where to start.
Probably we should try and incorporate DriveEncryption into Haiku itself and see about adding support for boot disks... that will require some discussion and agreement on how to change the bootloaders.
If we get a web browser with advert blocking, it will be ready for the modern web.