Greater Anglia
755 - think these are superb, really hard to fault them. Reliability gremlins were obviously a shame, but as with any new family of trains I'll give them time to bed in. Massive upgrade on previous trains and have made a mockery of other new rolling stock (particularly DMUs) with their accessibility, comfort and accessibility. They've raised the bar in terms of new rolling stock.
745 - almost as impressive as the 755, another good selection by Greater Anglia. As with most new stock though, not quite satisfied with the seating for longer journeys.
379 - comfortable seating (by modern standards anyways), good air conditioning and ride quality and plenty of space. Decent acceleration, well lit interior and connecting corridors between units too. One of the best Electrostars Bombardier made in my opinion (2nd or 3rd).
360 - Good, solid units. Acceleration is excellent so delays are readily recovered from, interiors are pretty much as good as a 3+2 seating layout can get. Not the most interesting of units, but they do their job well. Also reasonably reliable, if feeling a bit dated now (a refurb is overdue).
720 - the 3+2 seating feels really cramped in these (more so than many other units to be honest) and doesn't really fit the many Aventra principles such as walkthrough coaches. Acceleration, door opening times and seating capacity is excellent, but very little standing standing room. Passenger Information Systems and WiFi are good, but announcements annoying. Seating is acceptably comfortable, tables for airline style seats and leg room too (for the majority of seats, anyways). Interior feels of decent enough quality, but cheap in some areas.
321 - Similar gripes as the 317, but a slightly nicer travelling experience in general. The Renatus units are nice but I find the seating quite uncomfortable and the lighting a bit too bright and white.
317 - feeling very dated now. Strongly dislike the seating (I think the 317/5s have the type I mean) and find them very noisy, particularly in the motor coach. PIS is quite unhelpful, acceleration not fantastic and quite jerky and a lack of air conditioning is often really felt in the summer too.
London Overground
710 - very good at what they do. Acceleration, air conditioning, standing room and door size are all excellent for high passenger volumes. Good WiFi and USB charging points are a nice provision too. Not particularly comfortable seating, but these are not used on long journeys and the great ride quality and sound proofing help make up for this somewhat. I find the onboard announcements quite annoying, but it's not the end of the world.
315 - old faithful units, hard to fault these other than their age. Still accelerate pretty well, nicer seating than what is replacing them (albeit less room in peak time crushes pre-COVID) and reasonably reliable to boot.
378 - never really liked these. Interiors leave something to be desired, sliding doors are fast but make the interior noisier, unexceptional acceleration and air conditioning. Also really never liked the PIS screens.
TFL Rail
315 - see London Overground.
345 - similar to 720s minus USB charging (and in my opinion a nicer livery), but the length of journeys passengers are expected to travel on these units for is unacceptable. Nowhere for suitcases despite taking on Heathow services, seating that is arguably worse than S Stock LUL trains in terms of comfort (and what feels like fewer transverse seats than the S8s) despite longer journeys. Onboard screens feel poorly utilised.
c2c
357/0 & 357/2 - the perfect units for the job, but they need an overhaul (interior and mechanical/electrical). Air conditioning is still amongst the best in the country and ride quality is generally very good with good sound deadening. Many units have developed an extremely loud and unpleasant buzzing sound however (auxiliary converter module problem?), which never seems to get fixed along with broken doors between coaches. Passenger capacity is good, the 3+2 seating layout is acceptable in my opinion with good seat padding (lack of armrests justified, less so tables for airline seats), with some tables at seats of 4 welcome (although the 357/2s have unacceptably small tables). Acceleration is still plenty good enough, as is reliability on the whole with good passenger information systems and fast opening and closing doors. Interiors are feeling quite dated and are starting to disintegrate on some of the harder worked units.
357/3 - the "metro" conversion of 357/2s to form 357/3s has been a major failure though - reduced seating capacity has given way to standing room that offers very little to grab onto, often for "long distance" journeys (the LTS being on of the few routes that 3+2 seating makes sense on in my opinion). The grab handles they've fitted are also awfully rattly, particularly over rough track.
387 - decent trains, but are clearly not built for the route and are not really permanent solution. They are often downgrade on 357s on most diagrams due to lower capacity, slower boarding times and slower acceleration (they are too higher geared for this route). They are nice off peak for their tables, 2+2 seating layout with plenty of seats for 4 next to each other but in reality these are only used in the peak, and that is where they often struggle. Post COVID passenger numbers reduces this, but those "ironing board" seats and extremely bright lighting takeaway from what are otherwise very nice, comfortable interiors. Luggage racks waste large amounts of valuable space whilst PIS screens scroll too slowly for the number of stops these units often call at. Despite all this, I can well imagine passengers missing them when they are replaced by 720 units.