I have the '13 GS F Sport RWD with the 6-speed tranny. It's wonderful and I'm so happy I have the car. I've had some time with the car now and have spent a lot of time fiddling around and experimenting with the different drive modes in different scenarios.

Eco Mode: Mushy pedal compared to other modes, but still not exactly unresponsive. Suspension feel is softish, but not as soft as ES's I drove before buying the GS. If the car just drove like this, I think I would still like the car just fine. One nice discovery I made about driving in Eco is that if you're in slow, stop and go traffic, it's very pleasant to be in manual in this mode. The softer pedal response means much less lurching when you're trying to nudge the car forward in low RPM's, just discovered this a couple of weeks ago and I will use it this way going forward whenever I'm in this situation.
I use this mode about 10-15% of the time.

Standard mode: Pedal feel is slightly "better" meaning livelier than eco but still pretty plush. The car will more readily downshift if you depress the pedal a bit, and it will up shift pretty soon after you let off the pedal. Suspension feels just a smidge firmer than ECO, but if someone told me there was no difference, I wouldn't disagree too strongly. I think when you're driving reasonably, this mode offers the best combo of smoothness and responsiveness of the 4 modes.
I use this mode about 50% of the time - it's my default

Sport mode: Pedal noticeably more responsive, maybe even a bit jittery if you are heavy footed. Car downshifts pretty eagerly, and holds revs high for you momentarily after you let off the pedal after a hard acceleration. Suspension feel is hard to distinguish from standard mode for me. This is fun if you're doing random pulls - it's fun to feel the car kind of "wait" for you, ready to zoom away again if you get back on the gas. In manual mode the shifts seem maybe a little quicker when you're being aggressive, and the car does some small bucking if you "lug" it a bit at lower revs. If you want to go slightly faster than the flow of traffic and maybe execute a few passes on a relatively straight road, this is a great mode.
I use this mode about 20-25% of the time.

Sport + mode: Pedal feel is basically the same as Sport, maybe just a touch more sensitive. Downshifting and rev holding is more pronounced than sport, but slightly so. In manual, the car seems to attempt to "rev match" more than in other modes, and the shifts are reasonably fast. Suspension is noticeably firmer than Sport - more jittery over bumps and much much less body roll. Hitting corners hard is fun, and the car seems to shrink if you really chuck it into a tight turn at good speed. Steering is definitely heavier and better for higher performance situations. This mode is great at speeds over 80 and any scenario where you're coming hot into corners. Going through corners faster than you think you can is so exhilarating in this car! Having this mode available to you takes this car to the next level for me. The GS will never be as smooth as the ES or especially the LS, but neither of those cars has the little bit of edge this one does.
I use this mode about 10-15% of the time.

I notice very little difference in gas mileage when using the 3 modes. Maybe if I did long highway trips it'd be different, but that's not a thing where I live.

I know there have been some epic arguments on CL about exactly what changes as you go through the drive modes. To me it feels like there are slight but perceptible changes to the acceleration and suspension as you go from ECO through Sport +. The most noticeable difference to me is the suspension firmness and steering weight when comparing Sport + to any of the other modes. If I could change anything in the drive modes, I would make ECO mode even softer suspension-wise. It would be cool to have LS-like feel in eco, and still have the Sport + option on the other end. Maybe it's not feasible to have that much range in suspension adjustability, I'm definitely no expert on that.

Overall, the car is just amazing for me. I do not look at other cars with jealousy. I feel like I've lucked into a car that suits me so well, and I'm just grateful to have it. She's got 77,000 miles on the clock, and I want to get at least another 10 years of time with her.

 

I have a 2013 GSH, and I pretty much only use the ECO mode 85% of the time since for the most part I am doing the commute thing. If I go highway, it goes in Sport+ mode for the quicker acceleration and suspension stiffness. I thought the suspension only stiffens up in sport+ mode. At least that is what it shoes on the display. In either case, I enjoy the sedan and not having an SUV like every other vehicle on the road. I just don’t throw it around as much as it seems other people do. Guess I am like the NFL, the No Fun League. To my defense, Orlando FL is not a driver’s paradise. No hills, no open roads it seems.

 

Terrific write up on the sensations created by the Drive Mode selections, thanks gs350noob!

The ECO setting actually does quite a bit more than numb the throttle response. We can all
drive with fuel economy in mind ($5/gal fuel!) but we can not control the A/C compressor
or the cruise control responses. Both have a significant effect on MPG results. If you are on
a long drive on a hot day the reduced A/C output doesn't seem bad but short shopping trips with
lots of door opening and loading hot cargo and passengers will quickly illustrate how much
different the ECO is. Cruising on level roads in ECO is a great way to save up to 7% of fuel.
You will find when you are driving on hilly terrain that the throttle response is quite sluggish.

 

Thanks!

Didn't realize that about the AC. That's definitely something to consider. For my driving patterns, the highway fuel savings and improvement of cruise control mileage are non-factors, I've never even engaged the cruise control LOL.

 

Yeah, you definitely don't want to use ECO mode during hot weather, like it's been recently here in Dallas with well over 100° most days. The slower A/C compressor speed in ECO mode just doesn't cool the cabin down and get rid of the humidity fast enough - especially if you're in and out of the car often...

 

Great observations on the drive modes - I use Normal about 95% of the time! Only once in a while will turn the dial to Sport if i'm feeling like opening up the NA V6 (i have non F sport so no Sport+).

 

@AJLex19 - You aren't missing anything performance (engine-wise) without Sport+ mode. Even ECO mode at WOT delivers the same engine performance (e.g. fuel mapping, ignition and cam timing) as the other modes at WOT. When you go WOT the engine puters go full performance!