We have a 2009 SLK350. It's my wife's stylish and bougie commuter for nice days. We've had NA, NB, Z3 3.0, and 986 in the past.
Your expectation of 7/10 is accurate. It accelerates "good enough," handles "good enough" and overall is "good enough." Unlike the others, I would never even think of taking this one to an autocross or the FIRM to drive in anger. Sporty street driving during a commute, yes. A higher speed run through the Ocala Forest, yes. Seeking out twisty roads for a spirited drive, meh, nope.
It's as German and solid as the Z3, just not as willing to romp. On the other hand, the rear never wants to step out and try to kill you like the Z3 would. The folding hard top is wonderful, making it a real coupe when the temp is 110F, and doing its magic contortion in about 20 seconds to stow. There is a movable panel in the trunk to gain more space at the expense of not dropping the top. When the top is down there is a slot to get to the luggage area, but a backpack or small gym bag easily goes in and out. Groceries are no problem and there is plenty of shove space to load a lot of groceries in small bags with the top down. Good legroom and visibilty, small but ok cabin storage, cupholders suck like a proper German car. They are a fragile pop out set over the top of the radio and HVAC so when it spills gravity sends it down all of the electronics of the center stack.
I wouldn't do a SLK280 or SLK300, I think it will be <7/10. SLK55 is an option, but won't get you the price delta you're looking for.
In terms of the car itself, there was a mid-cycle nose change. We have the later front bumper with the styling cues from the F1 nose profile at the time. You'll want to find one with Air Scarf. It's the unique feature on these, so might as well get one. It is nice for cool weather top down drives. The subframes have been known to rot, but as 3rd or 4th owner I recently got my letter from MB extending the warranty for a few more years.
We bought at 63k, now 78k over 3.5 years. Purchased from dealer with warranty, and I'm ahead at this point. We had a major repair - they replaced a cylinder head for a misfire code that I chased but couldn't find. I felt vindicated but also that feels kinda flukey, but the total bill would've been $6k or so. We also had the AC go intermittent. Forums said there was a module that can be resoldered DIY. Dealer replaced the compressor and that module. I think this was fluff for "we don't want a come-back and warranty is paying" sort of thing. Wiring seems to be fragile. I replaced a headlight bulb (easy access through the fenderwell), and every wire I touched the insulation crumbled off.
A nice feature is the 2-stage hood struts. Open as normal and they'll stop at the typical angled hood opening. Continue to push and they'll extend to a service position with the hood almost at 90 degrees.
There are two sets of resonators and the muffler. We cut out one set of resonators and it gave it more of a sporty sound on acceleration but unnoticeable when you want to be bougie and stylish.
Even at 14 years old, I love the way it looks. We'll be sad when it's time to move on (likely this time next year) because it is a really good looking car.
You're an hour flight away if you want to test drive one :-)
