IMHO, agreeing with Kenny, they are arguably the best handling and sweet motored of the whole bunch, but with little character. The finish on the paintwork is not as good as the pre '81 machines. So there are a lot of rusty ones out there.
The pre81 frames have an undercoat, a heavy lead based light green covering which just doesn’t rust or wear through. The cylinder studs tend to pull out of the post 1984 models, possibly due to the inferior aluminum used or the original factory machining wearing out. The electrics are far better on later mono bikes, apart from the original dual output coils ( which should’ve all been replaced by now as the originals only had a short life due the bodies cracking). The mono rear wheels can be trouble, due to the brake drum being softer that the brake shoes. Easy to check, try taking the rear wheel off, the brake shoes expand into the drum and you can’t get the wheel off .. I find the monos bounce around more than the /7 bikes when riding them.
Never found them bad...but few years since mine was on road certainly nowt like as bad as the 'swinging' caliper on a 400/4. I always had a greased one ready to swap over as winter commuting was a nightmare...then add the hopelessly un-waterproof coils. Ah the bad old days