The OP is welcome to their view. As an ECML user, my own view is that IET is a mediocre train to travel in, that represents a deterioration in the standards that we customers are to be entitled to.
As a piece of traction, they are good and a welcome upgrade on what they replace. They allow acceleration of services and the bi-mode capability offers some useful gains in operating range. However, that gain is marginal and the performance issues on GWR and EMR show the limitations of bi-mode.
It is the passenger environment that lets them down. I like the airy bodyshell, and the seat pitch is an improvement on what was there before. But that's where the good news ends. The ride is appalling, and I have seen a number of people looking alarmed at bogie hunting on plain line. Then you have the seats. They are very uncomfortable, hard, and stiff - to say they're better than the 700s is symptomatic of the problem, as front line intercity trains should not be compared with the worst seating on the network.
I have then had too many journeys with heating either too high or, more often, too cold. Guards have had to apologise for this, blaming either coming straight off depot (perhaps) or inability to control the thermostat (more plausible, especially when the train stays cold the whole journey).
I might be tempted to overlook the procurement if it weren't for the fact that these trains cost a lot more than their predecessors, to deliver something no better.