Update time, a few more are coming to mind, defintiely dash board illumination as Duvel mentions and where water collects below the wing mirrors (I've noticed it to be a lot worse on the later (1989) editions with electric mirrors. There must be some trap near the seal for water, as all of mine with electric mirrors are as rusty as anything under there, the cars with manual mirrors, fine, despite being older!
Oh and the boot struts are definitely a major problem, I had often defended them, saying they'll wear out in any car, however the weight of the tailgate, especially with the spoiler on my GLT is far too much for even new struts in a slight breeze, as I found to my cost today. Loading the boot in a carpark today, I caught in the corner of my eye as I'm turned removing my hand from the boot to pick something else up, that the lid is falling rapidly. My mate who'd seen it fractionally sooner shouted, I withdraw my hand from the boot, only to get two finger tips from my left hand shut in the gap in line with the spoiler on the right hand side of the car, where I am unable to reach the boot catch easily to undo it!

As I was struggling to get my fingers out, my mate finally got to the catch and opened the boot, there was some seriously bad language

and my fingers had swollen up

I am now going to find some seriously powerful struts, even if it means adapting a stronger kind to fit! I want to have to hang on the tailgate to beable to pull it down from now on. A slight breeze was all it took, I was pretty lucky it didn't land on my arm or wrist, as that could've broken it, as anyone who has a boot spoiler will know what sort of weight is involved, especilally dropping from that height.
Well, I can't think of too many more bad points............yet, though for a car of this age, for only these sort of design faults, and bad points to show through, it's not too bad. There are some new cars that have a list as long as your arm of design faults and problems, and they've hardly been tried and tested or stood the test of time like the 300's have.
Pete