I didn't...
 

Well, I went to the dealer with the intention to buy the new gs. I test drove the car first thing and by 'surprise' I was disappointed by the road noise got into the cabin as compared to my 3GS. Also felt some vibrations around 65mph. It felt a bit jerky.
I just couldn't get my self to buy it. :-(

On the way home I was thinking... Maybe those Dunlop tires have something to do with it?

I'm curious to know whether the gs is using sound-proof type of glass all around.

the glass and cabin are vey well insulated. i have an F Sport with 19' tires and i hear very little to no road noise, depending on what type of street/road i'm driving on. you get more road feel with the 19's which i like. don't like to feel like i'm floating. the better the road feel the better the steering feel, the better the handling IMO. the dunlops probably are a factor as far as the road noise. my driver and passenger windows are double paned and the windshield is insulated. i have the ML system so the car is definitely well insulated.

Good for you. That is why test driving a car is so important. Keep shopping and let us know what you settle on.

My 4GS is much quieter compared to my 3GS. In fact, it is so quiet that I have to open the window to hear the street noise. Driving is night and day difference. It's smooth when idle, it's smooth in motion. Won't comment on handling as I'm sure you know what it's capable of :) Anyways, mine has Michelin tires.....

The double panes windows... is that an option?

I had the dealership swap rims/tires for me. My first impression was the same with the Dunlops. They had one car on the lot with Michelin MXM4 tires. I told them it was part of the deal or I was walking away. They agreed and I picked up the car the following day.

Look at tirerack review of the two different types of tires. I am not sure why one car on the lot had Michelin's and the rest did not. Both my car and the car with the Michelins were identical packages. Not sure if or when Lexus switched to the Michelins, but they are superior.

It is pretty loud inside at 65 MPH.I have Dunlops.I don't mind because I usually like playing the radio fairly loud.
I did experience the same vibration at 60-65 on my first highway drive yesterday.I was about to make an appt for the GS at that point but it went away after a few minutes.Haven't experienced any issue since.

I think the 4GS is noisier than my 3rd gen. But not enough where I thought it was obtrusive to the point of making a stink about it.

no it's not an option. i know the models equipped with ML, and i believe F-Sport models and Lux have the double pane windows. there is a thread with pics on here about the DP windows.

I drove a demo car before buying and the demo car had a wheel that was out of balance. you could really feel it when you got up to 70 or so. It was annoying but I knew it was not the norm. I bought a brand new one and it is smoooth and silent. love it!

Dunlops are the ones causing the noise and vibration. I felt it on some loaner 2013 GS. I drove others with Michelins and they are smooth at all speeds.

My F Sport has Dunlops. I have never experienced any vibration. The ride is as smooth as glass. However, there is some road noise over certain roads, moreso than with my Audi S5 that also had 19" rims. As someone else said, I just crank up the Mark Levinson up. I like the overall feel/smoothness of the GS. I don't want to be totally isolated, which is why I never went for the 3GS.

Anyone know if all gs fsport come with dunlops? I want michelin

Thanks for the responses. I think Ill ask the dealer whether they could swap the tires.

I have the Dunlops and they are very smooth, but the road noise is noticeable but not annoying. I will eventually replace them with Michelins down the road. If I had the choice, I would have chosen the Michelins.