I had the chance to sample 319362 from Manchester Airport on Friday, along with several Northern 142s, 150s and 323s over the weekend.
Having used to 319s on Thameslink many times, they are a known quantity and what I found on 319362 was of no surprise at all - it is a refreshed 319, pretty much unchanged from the TL ones I know and it did exactly what I expected it to... The compressor on 362 was a bit noisier than normal, IMHO.
In comparison with the 323s, a type I'm less familiar with, but still a fairly well-known class to travel, I found Northern's fleet to be in remarkably good shape and most certainly a level above their 142s and 150s. 323 acceleration notably better, as has been referred to many times, but the 319 was not exactly sluggish compared with the diesel units it is replacing.
The 142s I used, all the bus-seated variety were all fairly clean and tidy, again what I expected, nothing more, nothing less. In contrast, the 150s I used were notably very tatty, especially the long-term Northern ones (218 particularly), whilst the ex-LM ones were slightly better.
Overall, yes the 319s are better than what they replace (150s and 156s at present on the Airports) bringing extra capacity, hopefully faster services once the timetable can be adjusted and an overall better travelling experience. They are not a step-change improvement however, but they are more than adequate for the services they will be used on. The removal of the 5th row of seats to give 2+2 throughout would have been a good move, even if the extra cost of totally new seating, SWT 455 style for example, could not have been found (yet).
319s - clean (for now!) and tidy electric 150s, what else were you expecting?! Totally fit for the purpose, so the negative comments are unjustified in my view. Bring them on, lets get all 20+ in traffic asap, get some extra capacity going on their services and use that extra diesel capacity elsewhere. Finally, heading the right direction, even if a little late.