Conditioners such as Lexol and Leatherique are fine products but should be used on natural leather, not coated. They need to penetrate and "feed" the leather to be most effective. The vinyl type coating used on most newer car leather seats resists this penetration. The reason the leather is coated in the first place is to prevent the leather from absorbing spills, stains, dirt, etc. In so doing, it also prevents absorbtion, to a large extent, of leather conditioners. Some of the conditioner will probably get to the leather but as long as the coating is there and working properly, not much will make it through.
I noticed one of my stand-by products, Protectant 303, says it can be used not only on rubber and vinyl but leather as well. It does not smell like leather of course if that is what you are looking for but it softens the coating, gives a nice matte finish and the UV protection can not be beat (at least here in Texas that is very important).
I have a new Honda Ridgeline truck I bought in May of 2005 and have used the 303 on the coated leather seats and I've been very pleased. I also used Lexol and it was greasy, even after buffing. I simply squirt a microfiber mit with the stuff and rub it all over the interior. A bit later, I come back and buff it. 303 needs to have any excess buffed off or some areas may develop a chalk like streak, especially the dash. It can be sprayed on direct but the mit is easier and there is no chance of some accidently getting on a window. If it dries on glass you will have a hard time getting it off. I don't know how this will work out long term but so far, so good.