I'll second the leathermasters - but not just the cleaner/conditioner, but the protection cream. Helps you avoid stains.
I don't know if it is bad jeans or what, but a co-worker who had purchased his GS at the same time as mine has blueish stains on his driver's seat (he never used any conditioner/protection cream etc).
For cleaner, you really don't need to splurge. A lot of folks just use woolite with water (1:10) to clean their seats, and then use a good conditioner. Unless the seats are really dirty, you can just wipe with a clean damp MF towel to clean it. Apply the protection cream once every 6-8 months.