There are many flaws with this train.
The sounds are appauling. Clearly they have been rushed and fail to sound like any train in real life let alone the class 321. This is the only add-on where I have had to buy the Armstrong Powerhouse Sound Pack because the DTG version sounds attrocious.
The outside appearance is OK. I find the proportions are wrong, the sides are not slanted enough and the level of detail is just not worthy of a £12 add on.
Interior: Utter rubbish. Either nobody went inside the real train and so it is imaginary or the camera used to take the photographs of the interior to then put into the game was damaged in a way that changed the look of the pictures on it. Don't press 5 or your will utter many curses. The description reads "features passenger view" but what they forget to add is that it fails to represent anything meaningful.
So to sum up: The sound, interior and exterior fail to reach any standards of authenticity, userbility or value for money. The price of £12 (minus 1p) is a joke and under no circumstances should you buy this product at full price (or in the sale for all the reasons outlined above) unless you have money to waste and if you do have money to waste, don't buy this as it shows Dovetail Games that the product is good when it is far from it. I spent about £4 on it during a sale and even then it does not repesrent value for money. Really and truly do not buy this DLC. It is an utter joke on every level and at best could be described as a poor effort and at worst a complete rip off and money grabbing move by the makers. If you really want a realisitc class 321, go to Aromstrong Powerhouse. It is well worth the £15 (minus 1p) and is a real pleasure to drive. I hope that this discourages you from buying this DLC as it is a waste of money and time. Also, if you get it for free in your inventory, it is as welcome as the U2 album being automatically downloaded onto your iDevice.
Don't buy this product.
Because of the reasons outlined above, I will not be including it in any more scenarios (unless requested to do so).