First, there are a number of things that can contribute to a poor viewfinder experience..
Some of the early Zuiko's used thorium glass, wich can yellow over time. What is the serial number of your f1.4 zuiko?
What screen do you have? Coarser screens will 'pop' into focus faster but finer screens are smoother and may be brighter. -So it is not necessarily better to have a brighter screen.
You can use compressed air to clean dust the mirror and bottom of the screen. Do not ever touch either.
Silvered or aluminized glass of the mirror is extremely soft and easy to scratch. (really, if there are minor scratches from cleaning, I dont think it will be noticable.)
The bottom of the focussing screen is a plastic frensel. This is very delicate and can be scratched with a slight nick of your fingernail. Use plastic tweezers to remove. the screen type is a number printed on the tab.
Note that the OM1 shows 97% of the image, whereas the ME Super only shows 92%. This may be a minor difference, but it may contribute slightly.
-though quite honestly, even the newer zuiko's seem to me to be a 'warmer' than the smc takumars. It may be that the SMC coating, which I beleive is applied to all surfaces, may be better than Olympus.
-One thing that will make a big difference is to get a eyecup. It makes it much easier to see into the viewfinder without extraneous light.