There have been a few pictures posted that AGA have picked up on and gone 'which carriage number please?' to which I immediately think 'but they all look like that!'
I try not to post stuff that just shows somewhat threadbare seats - it's bad, but every train is like it and it doesn't impact passenger comfort all that much. Seats missing / broken off, however, I think is worthy cause for complaint. A bit like the campaigning for full replacement of every Class 321 - almost all of the truly terrible images posted are of Mk3s or 317s. The 321s tend just to have dirty floors (if it's an issue at all, a cleaning issue, not one of the rolling stock), litter (same here) or overflowing toilets, the latter I'll admit is nasty but again, not really a dealbreaker.
It's not a greatly popular view within the group but while I do think new rolling stock is necessary simply to deal with shortages and allow for potential service frequency improvements, I think replacing the 321s outright is a waste. What they do need is a proper refurbishment, to a somewhat higher standard than the demonstrator - by which I mean plug doors, a different model of PIS that doesn't perpetually go wrong, and an AC traction package. If every Mk3 EMU could be upgraded to this standard for a substantial cost saving over new stock, which I see no reason why not, I say they go for it - 317s first.
Ultimately, I'm mildly annoyed if my train is dirty or full of litter but it bothers me far less than even a 10 minute delay. I would argue service reliability is far and away the biggest problem with the franchise. If the shabby trains are responsible, time to fix that. Fact is though, like with the current Southend branch disruption, there's a lot more to it than that.