I've owned my R170 for nearly four years and I love it, but if asked I would say it's great except for the steering which is a bit rubbish. This is not, I believe, a radical new criticism of early SLKs.
I drive up and down an A road here on Anglesey quite a lot (A5025) and it's pretty poor condition. (I'm not sure what they spend my Road Tax on, certainly not roads as far as I can see - more likely bombs, but - whatever). It suffers from grooves where the surface has been worn away by tyres, and in the SLK this has been disconcerting to drive on, the car pulls into the grooves badly, and in general the steering could be described as vague.
I inherited quite good (looking) tyres when I bought the car, Kumho Ecsta SPTs with maybe 6mm of tread depth - but yesterday I decided they looked a bit worn on the front (nowhere near illegal, but far from great) so I had them replaced, with my local tyre depots recommendation of Nexen N Blues. Yes, I know, not the most well known of brands, and they were cheap, 2 for Ł100. I wasn't expecting much.
But... revelation! The tramlining has all but disappeared, the steering feels normal and no longer vague. It's like another car. A better car. I couldn't be happier.
So... okay I don't have long term experience of these tyres, but if you've got Kumhos fitted and the car likes to steer itself... get 'em replaced!
(Not that you probably would be interested, but I have a mini-site all about my car here : www.r953yau.co.uk