I've used Lexol, Griots, and Zaino. They all seem to work well. I have not noticed any residue or more sheen from any of those products.
I usually apply the conditioner a minimum of 2-3 times per year.
I used Leatherique on my M5 last year and can't say I was impressed given the cost and time it took to apply the product (I'll probably get torched for that comment from the Leatherique faithful). I'm not saying its bad....for me I couldn't recognize any additional benefit it provided over the others I mentioned given the effort and cost. Perhaps I didn't recognize any additional benefit from the Leatherique because I condition my seats a minimum of 2-3 times/year.
I think any of the products that have been mentioned in this thread will work well.
2012 BMW X5 Diesel Platinum Bronze Metallic/Black Nevada Leather/Dark Burl Walnut Wood
M5 Oxford Green Metallic/Caramel/Dark Burl Walnut Wood
2010 Range Rover Supercharged Ipanema Sand/Sand with Navy piping
2006 Range Rover HSE Buckingham Blue/Parchment with Navy piping/American Cherry Wood....gone but not forgotten
2004 Toyota Sienna XLE Bronze/Stone....gone but not forgotten