Hi aslowdodge and welcome. It is generally accepted that the earlier the R230 (SL series from '03 - '12) the more trouble prone they can be. This is particularly true of the ABC - Active Body Control system. There were improvements in '04 and/or '05 which help in the longevity department (the crimp connectors on the hydraulic hoses for instance). I bought a 2005 as I felt a little extra money for a few years newer would be money well spent. 2007 should be that much better.
These cars are generally very reliable considering their extreme complexity. There were some issues early on but recalls and repairs should have taken care of most of these issues by now. These early issues don't pertain to a 2007.
If you decide to purchase an extended warranty PLEASE read VERY CAREFULLY exactly what is covered under suspension repair. The majority of issues (especially expensive issues) come from the ABC suspension system on the R230. Be certain any extended warranty you buy covers replacement of dampers (shocks), ABC pump, and hydraulic hoses at a minimum. Ideally accumulators and valve blocks would be covered as well. If this is not clearly stated be sure to ask in writing and if the company agrees these items are covered than hold on to that paper!
IMHO an extended warranty on a R230 that doesn't cover the ABC system is wasted money.
That said, a later car like a 2007 should have minimal issues to begin with.
Also, many of the issues that pop up with the ABC system can be prevented with routine (every 50,000 or so miles) fluid flushes and taking care of problems at the very first sign of any trouble. Small issues can get real expensive real fast with the ABC suspension.
That said the SL is a fantastic car.
Let us know what you decide,