I bought the Acela back in 2013, and boy am I impressed with the updates they have made. The Acela now has the current Acela paint scheme, so if you want the previous version, hopefully you have a backup of it somewhere.
I'll point out main things they have fixed:
Horn - Big issue for me. It looped correctly in the cab, but did not loop at all in the exterior mode. They also changed the horn, makes it sounds much better.
X360 Controller issues - For me, I could never leave the cab in the Acela using the controller. You could use the functions fine, but as soon as you wanted to transition from Cab view to outside view, it wouldn't change. This also happens with a few locomotives I have now. Everything is fixed now, works great on a controller.
Features they added:
New Headlights - Headlights look much better now, they have a really nice Lens flare that appears when you are in front of the locomotive. Real nice touch.
Pantograph Sparks - This may seem like nothing, but this feature is really cool. As you drive along, you can see spark reflections on the pantograph. It also emits a big area of blue light around it, and looks really nice. I personally think it emits too much light, but is still a nice feature.
They probably have fixed and added more features with this loco, but I'm really liking the update for the Acela. It once made a beautiful model suffer from terrible scripting, to an absolute model with great scripting and features. The only thing I can think of to add to this model would be an interior for the coaches, would be a fantastic addition.