Long time lurker here, just took my first couple of rides in the 700 over the past week, so I thought I'd post another review because I think previous posters missed a couple of things. Both trains I caught were delayed 16:51s from Farringdon to Brighton, although only the first was due to delays caused by the train itself - this time due to the doors not opening for 10 minutes at the platform.
My comments about the experience:
1) The seats are indeed as bad as I had feared after reading many a post in this forum. I hopped in a window seat initially, but then quickly realised that my legs could not fit without wedging them right against the back of the seat in front of me, forcing me to sit at an angle to the detriment of the passenger sitting next to me. The high window provided no arm rest either, and as the passenger beside me noticed my discomfort, we swapped seats and I was surprised to note that the aisle seat had about an inch more room to the seat in front of me (it's possible that the seats aren't perfectly aligned to the wall). I'm fairly tall though, but I was talking to a fellow commuter who is less than 6 foot who also found them rather uncomfortable. On a later train I had a fold-up seat near the toilets, which doesn't offer any leg room if you don't want to trip people over, and quickly become uncomfortable due to how low it was to the ground. Never was much of a fold-down table user, but I really miss the armrests. Still have yet to try out the single seats.
2) The lack of a carriage divide plus the easier-access doors on every carriage has the consequence that very young children and prams seem to be evenly-distributed compared to a 387 or 377 where they previously were located only in the toilet/bike compartment. Not a huge problem, but if you're a commuter, you might want to consider a decent set of headphones, as there is no escape from such noises as there had been in the past.
3) The second train I caught was after a series of large delays and during the stikes this week, so it was at a crush-loading level after Blackfriars, and even more after East Croydon. While the number of people that could fit on the train was impressive, the carriages were so wide that you had nothing to hold on to except the people around you, which on a 377/387 or even a tube line you can at least grab a overhead rail. They might want to think about adding them IMO, as the jolts while travelling or accelerating are still very noticeable.
4) On the fully-loaded train, my normally fine internet connection was extremely bad the whole way. I'm guessing this is possibly due to the overloaded towers, and the number of standing passengers having nothing better to do than to read their phones. With the increased capacities these trains offer, I hope the cell companies will keep up, but I doubt they will anytime soon.
5) The air-conditioning has been good so far, I experienced none of the freezer-like conditions after the aircon has been turn on when riding a 377/387.
6) Noise and general travelling experience was good, they are certainly quiter and quicker because of the lower weight.
Overall and tl;dr, it's a good train for perhaps crossrail or short hops, but it's a noticeable long-commuter downgrade from the 387, and even the 377 in parts (never was a fan of 3-2 seating). I can't see anyone commuting long-distance liking them, with the lack of plugs, tables and arm rests. I personally think it's a better idea to run them between Gatwick Airport and St Albans where the need for total passenger capacity is high, and the average travel times are more in line with those experienced in Greater London. You could run them to Brighton in the weekend if needed during peak times. It just seems strange that Gatwick Express has the 387-2s, while longer regular commuters have the more airport-traveller-friendly 700s.
