IMAX' use of two 2K projectors and an IMAX-specific DCP in 2D operation is more about hiding the pixel grid than anything else. To me it seems more like the operators just nudge the projector a little out of focus to blur the image a little bit. This goes for all giant screen d-cinema theaters. The IMAX specific DCP isn't all that special for 2K. And it's no different for dual projector 3D. Again, IMAX doesn't have the only dual projector 3D system in operation.
Viewers aren't seeing any more image detail in IMAX than they would in another theater. When it comes to 2D they might be seeing less if the movie was produced in 4K. The only exception is when a movie, such as Skyfall, has a taller image that fills the entire IMAX screen while the other theaters get a vertically cropped 2.39:1 version of it. However, in the case of Skyfall, that movie had a 4K digital intermediate and 4K DCPs (uprezzed from Arri Alexa 2.8K cameras). For 2D movies, I consider IMAX a waste of money unless I'm watching a real 15-perf 70mm IMAX movie in 2D.
I'm not going to say the digital projection in competing premium priced big screen theater concepts is superior to IMAX' d-cinema projection. I'm just saying IMAX' digital stuff ain't all that great.
Please note, I flatly refuse to call any of this d-cinema stuff "large format." A bigger screen does not automatically make a d-cinema process "large format." It is no more large format than someone pointing an ordinary 4-perf 35mm projector at a 15/70mm IMAX giant screen and projecting a 35mm print on it. 15-perf 70mm film projection is a real large format process, especially when the material was originated on 15-perf 65mm negatives. 8-perf 70mm is a legitimate large format process. I might even be willing to go so far as calling classic 5-perf 70mm a large format process.
For me to call a d-cinema system "large format" it has to do more than offer the same old HDTV resolution image blown up on a bigger screen. I want the movie shown in 6K or 8K resolution with native resolution to match that high level. If they shoot the movie on 5-perf 65mm film offering a 6K or 8K digital intermediate would be no problem. Some digital cameras can do 6K or 8K. All the commercial cinema systems currently max out at 4K for 2D and 2K for 3D.
Back on the audio side of things, IMAX is falling behind even in terms of speakers behind the screen, not just the surround sound.
Dolby Atmos allows for 5 speaker towers behind the screen, just like the classic Todd-AO 70mm system (and the not often used SDDS-8 layout). Since Dolby Atmos is object based it wouldn't be much trouble for more speaker channels to be added behind the screen.
The Auro 11.1 format has its standard layer, height layer and ceiling layer. While it only has 3 primary channels of audio behind the screen, all 3 of those channels have height layers added to them. So it's really like three pairs of audio channels placed behind the screen.
IMAX just has three speaker enclosures behind the screen -just like all the standard priced theaters.