Yes, over the past year I've noticed steady improvements. I recently re-downloaded Arkham City to mess around in the challenge rooms after getting the itch from the Arkham Origins Quick Look and the download was done in about 2 hours. The Last of Us did not take very long either, at least for a file of that size. Maybe two and a half hours/three-some hours, which doesn't bother me as much as it would some. Seems reasonable for the file size.
edit: I'm on a 20mb down connection with a speed boost up to 25 for large files, by the way. But I usually get speed tests in the 15-18 range.
Yeah. I remember when the Instant Game Collection got announced and I put Ratchet & Clank: All 4 One to download. It took a very long time and it's 14 GB. I downloaded Kingdoms of Amalur which is 13.4 GB a couple days ago and it took a fraction of the time compared to R&C which was June 2012.