It is not a BMW 550i, but it comes quite close in terms of handling. Interior materials are a bit superior to those seen in a BMW, especially when it comes to sound. Given Lexus/Toyota high levels of reliability this vehicle was a better choice for me.
I recently purchased a certified GS450h. It is in excellent condition and having the 161 pt check done gives me peace of mind. I am blown away with how fast it is. A friend with a Porsche drove it and said it is much quicker off the line. The lines are great and I love the the design hasn't changed, so you can't tell that it isn't brand new. Got to love the Lexus Experience.
My wife and I decided to go from 3 cars to 2, so we traded in a 2001 Accord EX V6 and a 2003 BMW M3 for the GS 450h. We ended up with a car that carries people better than the Accord, performs better than the M3 (really), and gets better gas mileage than either (we get between 26 and 27 mpg). If you drive it like a high-powered sports car, it will perform like same - right down to gas mileage in the teens. If you drive it like a sedan, it will give you all that plus another 5 mpg. Visibility is excellent. Controls are perfect. Everybody can find a comfortable seating position.
The performance of this car is mind-boggling. If you floor the gas while driving at 70 to 80 mph, you WILL get pushed back into your seat and blow by everything else on the road. If you are over 6 feet tall, you should definitely sit in a GS before purchasing, especially if you tend to sit straight in your seat. I'm 6' 1" and my head touches the roof. The trunk is definitely tiny, but I personally do not place large suitcases or any other significant cargo into the trunk on a daily basis, so this is a non-issue. For trips to Costco or the airport, we just use the other car, an SUV. The navigation voice recognition takes some practice, but otherwise the nav system itself is powerful