First off, this loco is probably a 4.5 star model, only losing the .5 to a few minor issues.
Firstly is the difficulty of separating the loco and tender to place a DCC chip. To do this you need to disconnect the large electrical connector between the loco and tender, this is tricky and you are at risk of damaging small details - of which there are many. Reconnecting these is equally as hard but is well worth it.
The only other issue I have noticed is that the middle tender wheels tend to lift off the track on the sharper radius of curve. This hasn't noticeably impacted performance but is something to take note of.
As for the positives, of which there are many, the etched plates are fabulous, as are the crew. The detail is immaculate and the loco is happily navigating my small layout.
A final thing to note is that the non - sound chip disables the firebox by default, I found that 8 worked to switch it back on.
Overall a great loco and I would recommend.