But as a new member to GT its hard to not compare. I think both have their strengths and weaknesses. I have some recommendations that would make GT even better if you don't mind hearing them.
A few for now, more later:
Metronome - It would be nice to have an option not to accent a note at all(is there a way) so you can just have a steady beat- I was originally taught on a metronome to not use accent settings at all especially when practicing 16th note alternate picking(looks like your old metronome had that option). Would even be cool to able to make a simple drum pattern loop(I usually practice to a drumn machine). I know the metronome has different sounds but you can't make a drum beat with it.
Bookmarks - It would be nice to be able to organize these into subfolders and also add personal notes of progress etc. I find myself bookmarking alot for lessons I want to work on at another time and not forget about, but then my bookmark folder just becomes one huge overwhelming list which is unmamageable. GMC used to do it the way you have it , but recently added more advanced organization and everybody loves it.
Backing tracks for the lesson(I believe some might already have this), not just an mp3 of the lesson. After learning something, its nice to be able to play a backing track loop to practice the new skill, but also list the chord progression of the backing track. I think its important understanding the theory of why a progression works with a particular scale/pattern(slowly ingrain theory). GMC was good at stating multiple scales that would work over a partcular progression.
More visuals of fretboards(Notation and tabs are great) , but it important to also see the relationship on the fretboard to help it stick (I know some lessons use more fretboard layouts).
Just my initial thoughts - hopefully it will help on further development of GT.
Let me know if you have any feedback or questions(Or if I a mway out there).
"I learned a long time ago that one note can go a long way if its the right one and it will probably whip the guy with 20 notes." Les Paul - 2002