The manual says to use a damp cloth to clean it and not to use a leather conditioner. I don't listen too well, though. I used a professional leather cleaner and conditioner to no ill effect. IIRC, someone used one conditioner that ended up filling in the perforations in the leather, which they were not too pleased about.
There are tons of good cleaners and conditioners out there. The most versatile combo I have yet to find that offer a great smell and excellent results is probably the Zaino Z9-Z10 combo. For a grippier texture but an odd smell, I like Sonus leather conditioner. I have never been a fan of the black leather interiors on these vehicles. I detailed an '07 Exige S with only 160ish miles on it, and the leather looked really bad...it looked like cracks were starting to form. Oddly enough, the other interior colors do not have this problem as much. Lastly, if you have the money, try leather masters or leatherique products, especially for more neglected leathers.