Opinion amongst many in the rail industry is that Abellio were fools for deciding to do this. Quite apart from the fuel it's added to the Scottish nationalists' perennial sense of grievance ("they're 40 year old cast offs!"), the refurbs have been fraught with difficulty, they're hugely fuel-inefficient and expensive to run in short formations, and, as has been pointed out many times, the bodies closely resemble Swiss cheese. Rumour has it that the person responsible for pushing the HST option within Abellio is an HST enthusiast who has allowed heart to rule head, and it's turned out, in my opinion, to be a very bad decision.
All it effectively does is kick the can down the road in terms of rolling stock replacement, and just creates a problem in a few years time, rather than conclusively solving it now, which could have been done with new rolling stock. There's plenty of suitable designs out there that would have improved comfort and capacity, have been cheaper to operate and would have lasted a hell of a lot longer, while being more energy efficient and eco-friendly. The HST has turned out to be a very, very bad choice here.
I'll grant you they're nicer to travel in than Class 170s, which are not bad trains but not ideal for long journeys, but that's about all they have going for them.