We've owned Lexus, Mercedes, BMW, Jaguar, Audi and Infiniti. Comparing the Lexus to the others, here is what I feel.
Mercedes: Mercedes does a great job on the feel of the car. Interior materials and design is tops. Suspension gives you a great feel and isolates you from the road - incredible mechanical engineering. Easy to drive. You don't feel fatigued after hours behind the wheel. Some parts are very reasonable, others are horrendously expensive. Labor is high. Lexus beats Mercedes in reliability, cost of ownership, resale value and maintenance. Mercedes beats Lexus in performance, driving, interior, exterior styling (my opininon) and easy to drive. I also feel safer in the Mercedes. I think Lexus is shooting for Mercedes.
BMW: More of a performance car. If you want to feel the road, this is the car. Great drivers car. Can't compare it to a Lexus. Cost of repairs is high. Maintenance gets really high as you pass 100,000 miles. As they say "the ultimate driving machine".
Jaguar: Jaguar just feels good. So sexy! Great comfort. Seats are to die for. Leather everywhere! Ergonomically a nightmare, but who cares? Looks great - make that phenomenal! I love my Jaguar (s). They make funny noises, dash lights come and go randomly. Sounds like an airplane when driving on the freeway. No major repairs yet (116K on one we no longer own and 59K on the other). Maintenance is expensive. Parts are expensive. Quirky, but what a dream car. No comparison to Lexus - aimed at two different markets. We had an XJ (gone now) and currently own an XJ Vanden Plas.
Audi: Some people love Audi. I prefer BMW to Audi. Both are good driving machines, but BMW does a better job. In bad weather conditions, the Quattro system is incredible. Nobody has an all wheel drive system as good as Audi. I don't think you can compare Audi to Lexus either.
Infiniti: Love the power! Had an M45. BMW out handled and out drove the M. The M would walk away from our 540i, but had to slow around corners. Hard riding suspension that is not designed right. Lots of problems with the car. I think Lexus beats Infiniti hands down. I made the mistake getting an Infiniti vs another Lexus. When the Jaguar starts costing us too much in repairs (hopefully won't be for a long time), we're going back to Lexus. ES, GS, LS - any will be fine with me. We still have the BMW which fulfills my needs for driving performance, so a super reliable car will be a good match (Lexus).
In a nut shell, Lexus produces the finest luxury automobile in the world. The only downfall is that they feel more like appliances than a car you love (personality). I think the Japanese have engineered this car to perfection, but they forgot one of the ingredients - in this price point you want to love your car. People who own European cars have a love hate relationship. They love the car because the feel/drive so well. They hate the cost of ownership, depreciation and reliability issues. I don't know anyone who can say they love the character of their Lexus. They love the reliability, smoothness, quiteness, etc. For those who say they love the luxury, they haven't experienced a Mercedes or Jaguar. Lexus cars look nice, but they lack the class of a Mercedes or Jaguar. They don't perform like BMW's or Audi's. So, it depends on what is important to you. Do you want the ultimate driving machine, the ultimate luxury vehicle or the best engineered luxury appliance on the road.
Good luck with your decision.
I hope this helps.