The new version also has improved subsystems and supporting libraries, enabling non-native applications to be ported from Linux, FreeBSD and OpenBSD. It has translation layers for both X11 and Wayland, as well as for Gtk apps, alongside the WINE support it gained this time last year. This means a number of new apps, including the GNOME Web browser Epiphany, a full graphical version of Emacs, updated POSIX layer, WINE, and more.
This version is built with GCC, but which version of GCC depends on which edition of Haiku you choose. There are both 32-bit and 64-bit versions. The x86-32 edition is still built with an ancient version of GCC, because it remains binary-compatible with the final x86-32 versions of BeOS. If the Haiku developers move to a newer GCC, that will break backwards compatibility. At some point, though, the x86-32 version will probably go away. The 64-bit version is built with GCC 11 and ran flawlessly on an old BIOS-based ThinkPad and in VirtualBox.
A nice review which also touches upon some BeOS history.