erchou: Ok, maybe this is a silly question, but could anyone who has tried GemRB tell me the advantages/improvements/new stuff it includes? I checked the site but it doesn't say much.
Not too much as far as Windows and the original games go. It's mostly of concern to modders and people wanting to develop new games with the engine (or, of course, poeple who want to run the games on non-Windows/x86-compatible platforms).
New stuff include support for OGG audio and PNG images (rather than just WAV, BMP, and the various proprietary formats used), making it possible to compress game data a bit and giving more possibilities for mods and new game projects. Other improvements concern mostly other platforms such as phones and tablets with multi-touch hardware. GemRB also externalises all data that were hardcoded into the original games' exe files, making the engine more generic and the data available as files giving modders the possibility to modify them at will.