While hardly the biggest changes, the main highlights are the worldmap and action handling improvements that make HoW playable. All the stores and temples now function properly, while in BG2 users are more likely to notice that summons now have full actionbars of their own - spellcasting summons and illusions are not useless anymore. Also noticable are the sound improvements (no more death sounds on load) and the much less buggy sparkle graphics.
Currently only the sources and linux binaries are available. You can get the sources here. The linux binaries are in rpm format, built for OpenSUSE, but should work elsewhere (can be extracted with rpm2tar and others). Get them from here.
Full changelog digest:
GemRB V0.6.3 (2010-11-21) New features: - IWD:HoW is now completable! - casting sounds and footsteps - autodetection of secret doors, detect illusions - basic bardsong support and selective magic resistance (bg2-style) - proper store economics, ergonomics and dragging - custom blood color (creature-dependant) - new actions, iwd effects and triggers - Importing a SoA game into ToB Improved features: - actor selection and action bar (for summons and illusions too!) - door bashing and traps - loading screens, ambushes, worldmap - sparkles, panic and other effects - actions, dialogs, object matching - personal items support (swap/equip/remove) - bugfixes Applied patches: iwd regression fix from Eggert Jón Magnússon