I can well imagine the enormous work involved in trying to pull together a set of rules and supporting material in a way that could bind together the devotees of both the 5.5 and 7.5 editions. So - the wait may have been longer than we would have wishes but the job is now done.
The first pdf version (there will be another correcting the inevitable typos) looks really splendid.
I haven't had time to read that much in detail but it is well structured and very well presented. It has humour and it gives choices.
The spellbook has been carefully revised and inconsistencies and lack of clarity addressed. There are fewer L1 spells than in 7.5 and some spells (eg Little Feets and Vorpal Blade) and Oh Go Away can now affect multiple targets for higher level wizards. Although the Khaboom Wizards' Guild will continue to do things a little differently, I think they will understand the revision in distant Khazan.
Specialists have been reworked so that they actually make sense! Fantastic!
The learning of languages looks to be a masterclass and does so much more than removes the non-sensical approach of 5.5.
There are some things I think I will resist (because of games work consistently well another way): we will keep the INT check for spellcasting and we won't completely ditch the concept of adding level to saving rolls (maybe only for WIZ and LK SRs).
Although there is a lot of detail, a lot of pages, it does not look as if it should be daunting to a newcomer because of the strength of the structuring and the clarity of the layout.
More later, I'm sure.
(Oh, and the artwork rocks!)