At the moment when everything runs OK the high-peak trains are absolutely fine for getting a seat. The 1724 is always mobbed, yes, but the 1713 is deserted (it skips Hemel and Berkhamsted) and 1730 is usually relatively quiet in the last two carriages. I get to Euston about 5-10 minutes before the train and only fail to get a seat when a train is short-formed.
It's the shoulder-peak that's bad. The 1634 used to be just about OK as a 12-car so London Midland, in their infinite wisdom, cut it to 8-car. The 1654 used to be OK too, but now it's an 8-car 321 and it is rammed.
Saturday mornings are the worst though. A 4-car 350 is the norm for the morning trains into London, and they're always full and standing after Watford. I guess it costs London Midland money to run the extra carriages.
My concern is when they lose the equivalent of two 321s. The only way they'll claw that back is by cutting carriages off other trains. My train in a morning- 0803 off Hemel- is usually relatively quiet as a 12-car (usually four people in a 6-seat bay on a 350/2), but when it rocks up as an 8-car it is full and standing. I don't see how they can keep everything as a 12-car with the loss of two units.