We were at the BWV 12/5 - 12/14 and used the IG pretty much every day at various times. The Skyliner was running consistently the entire time we were there (AFAIK). Many guests from POP/AoA & CB as well as those who just wanted to experience it were using it. There weren't many empty cars running by us in the mornings or evenings.
The IG was certainly busy, but honestly, it didn't take us any longer to get through the lines and into the park than it did last year at this time, even if we arrived just after a boat unloaded. (We always walked from the BWV). Disney enlarged & improved the access and added more staff there, too. I liked that they had a "no bag" line and a special line for strollers and EVCs/Wheelchairs.
I won't be popular, but I wish they had a special line for back packs - lines with those moved a whole lot slower than even the
ECV / Stroller line. Can't imagine why anyone would want to carry those stuffed bags around all day, either. I sure wouldn't.
Anyway, IMO, the worries about delayed entry at IG is overblown. YMMV.