Had this since TS2012, but it's been changed/revamped/retrofitted/whatever word you want to use since then. Some changes good, some not-so.
From what I've observed overall, the unit is very easy to control as one'd expect, being a MU. Visual and modeling details have always been a personal high point, with the animation being good, too. Some touches are here and there like the panto sparks, updated livery, and the lens flare as another user has noted. I wouldn't be absolutely sure but I think the specs have been redone since then too, like how in the past it'd top out at 147 MPH in the sim, when the real one, as also noted in promotional material of this DLC here and there, can go up to 162 or 165. Seems to speed up a lot faster so it can be assumed they gave it a bit more juice.
Other bugs have been fixed when you load a scenario partway through that had to do with the Cruise Control, displays, and other cosmetic functions. The "Acela Express" scenario was also optimized a while ago, although the last time I played it, it still suffered here and there from an AI train desyncing and derailing offscreen, the player being held up at Newark by a signal and thus not be able to satisfy the timetable, or be unable to finish the scenario at all with a set of points always set against you.
If you also own or plan to own the New York to New Haven DLC, there are a few more Career Scenarios available using the Acela there too, although the Achievements seem to be broken at the time I write this.
Now, some of what prevents this DLC from being more perfect (in my eyes, anyway):
- Cruise Control is broken; it either takes longer to kick in than from before this DLC was reworked, or it doesn't at all—the Class 390 is a better example of how it should function.
- Pantographs can be a bit wonky; by default, the front pantographs are used relative to the direction being traveled, when it should be the rear ones. The cab switch to choose a pantograph doesn't appear to be animated either, and whatever I do seems to cause an indefinite loop of raising and lowering the "unused" pantograph.
- Carriages leave a lot to be desired; while I did note the modeling was nice, inconsistencies from the real thing include the lack of the Business Class "End" Car (it's like the First Class Car, with two doors rather than four), how the carriages are generally flipped as opposed to how they should be in consists (ex. the First Class Car's—and wouldbe Business Class End Car's—doors should be adjacent to the Power Car, the two middle Business Class Cars, seat-wise, should face away from each other, and the Cafe Car should also be flipped relative to how it currently is (to give an idea, the windows, on the side with less windows, should be closer to the closest Power Car)).
- In addition to above, they lack a passenger view.
- The horn does not automatically turn on the bell like it does on the ACS64 (as well as how it did in the original Kuju/MS TS).
- Whatever updates done to the DLC also messed with the lights; the marker lights (the red ones) on the opposite power car don't always turn on when the front ones are switched on, and the ditch lights can either be on or off; they don't flash or alternate like previously (at least for me).
- I probably don't even need to mention the sounds, save for the horn and bell really (though, this is only minor personally).
Otherwise, it's a must-have if you're going to drive on either of the Northeast Corridor Route DLCs, especially when you consider the workshop scenarios available here for them. Too if you just like fast trains like I do.