I've used several. What works best depends on the type of leather you have. For older surface-dyed leather, Leatherique seems best. Ferrari used surface dyed leather through the early 90s, and it's basically a spray-on color that attaches to the surface of the leather like spray paint. It looks nice but cracks easily and tends to help leather dry out because it can't breathe through it. Leatherique makes a cleaner (Pristine Clean) and a conditioner (Rejuvenator Oil) which are great for surface dyed. They also make a good line of dyes if you ever need to refinish an interior. The owner is a car freak (organized the Aiken Car Show last weekend) and owns a TR and some older Rolls.
www.leatherique.com
For newer leather which is vat-dyed (not just sprayed on - dyed all through the hide), I like the Color Plus system. This is what Ferrari switched to and what my Diablo has. Not sure about earlier Lambos. They also make a cleaner and a conditioner which are excellent.
www.colorplus.com
Lexol and Hide Food are ok conditioners, but they have a high percentage of water, which is basically a waste. You will have to apply Lexol or Hide Food much more often because there are fewer oils in it by volume.
Lastly, one of the most important things when you treat leather is the cloth you use. Do NOT use terricloth towels. I learned this the hard way as terricloth, even if it feels very soft to you, will rub the surface dye off of leather. Soft terricloth is still equivalent to a 400-grit sandpaper. Most leather care specialists I talk to recommend using OLD t-shirts for treating the leather - the kind that have been washed so many times that they're soft almost to the point of being threadbare.
Good luck!