No one in the TeX world seems willing to touch this stuff. It’s radioactive. Xdvipdfmx still doesn’t write the useful ToUnicode maps, I think, but that can easily be remedied. I just haven’t gotten around to it. Adding meaning ToUnicode support to ConTeXt Mark IV was pretty trivial, and I haven’t bothered to supply my patch mainly because I expect the developers to get around to it themselves, once the design has settled down some. But the free GUI-oriented stuff that is out there is hard to stomach, and it irritates me even to try to help improve matters.
Seriously, there is much really wonderful development in the free software world, such as the operating system I’m using, which makes Microsoft Windows look like a pile of dog crap, but the ‘mainstream’ software for production of text is incapable and bad. Hang onto your Adobe CS.
Late edit: Mind you, I suspect that the ‘glyph clusters’ may actually serve a purpose in some non-latin scripts, like maybe arabic with all its incredible fanciness, and they may also be useful in some unusual cases with Latin scripts, but I haven’t found such things necessary when making e-books.
Late late edit: I don’t want to be un-nice, and much of the free software works pretty well for me, at least with my patched-up fontconfig and if I don’t try to do anything fancy, but I feel released to rant like this because Adam Twardoch, a name well known in the font community, already had a similar rant a few weeks ago in a FontForge mailing list. He was particularly annoyed about Scribus. (His annoyance with FontForge was FF’s crashiness, although that at least is a documented misfeature. :) )