I work for Northern and the 158's are our best units by far, I tried to post previously some of the reasons the air con isn't always great and why they aren't repaired as often as needed, why we don't "rip out all the windows for new windows with more quarter lights" (idiot) and was shot down in flames. However, the 158's for 24 years old are not bad at all, they do have air con, which even if it doesn't work makes it no worse than the other sprinters and pacers. They have the best ride due to having lateral dampers and shorter, stiffer springs. The seating is much more comfortable in the saloons. They have three toilets for those boozey last trains. And they can run at 90mph rather than 75mph.
And just to follow up to the comment, "I'd rather be on a 142" you are clearly the reason they still exist, instead if we were inundated with complaints eventually the government would have to commission rolling stock to replace them from pressure from the TOC running them, it would take a long time and a lot of complaints but I would much prefer more 158's over pacers or earlier sprinters.