I recently finished reading the DxO review for the 5D Mark III. While I am not a huge DxO fan, and I take their results with a grain of salt, I do pay attention to their numbers. I was willing to be rather forgiving of Canon for not producing a better sensor in the 5D III (and I suspect we'll see similar results with the 1D X), as they offered so many other enhancements beyond IQ.
However after seeing the results all over the web (not just at DxO) for the 5D III, and checking the raw numbers at sensorgen.info, I am rather concerned about the trend in Canon sensor technology (particularly given the increases in cost...a $700 difference in price is really rather shocking). For all their talk, Canon seems to have barely managed to maintain the status quo, and has taken a rather alarming step backwards in terms of low ISO read noise (according to sensorgen data, a whopping 20% step back!) I awaited the 5D III with baited breath, and while I was ecstatic about the AF, VF, and host of other physical improvements, I decided to wait and see if Canon announced their own high-MP camera with better IQ. For my landscape work, more megapixels and higher DR will really do wonders. However therein lies my concern... Will Canon release a high MP pro DSLR that has the same horrid low-ISO read noise as the 5D III? What about other future Canon cameras...the 1Ds X? The 7D II? The 5D IV or perhaps a 3D?
I'm thoroughly invested in Canon lenses, and as such, I'm pretty much a Canon guy. I like my gear, and love the innovation Canon puts into its lenses. I love the fact that they have some very unique optical technology like the MP-E 65mm 1-5x Zoom Macro, TS-E lenses, Diffractive Optics in small, lightweight packages, and the stellar quality and nanocoating of L-series glass. But a 20% step backwards in terms of low ISO read noise in what is supposed to be the top of the line pinnacle of Canon sensor technology...is completely unacceptable to me. Its great to make improvements to a sensor, but not at the cost of performance elsewhere...trade-offs don't make for good sales pitches when the competition is making headway on every front, and I've reached the end of my available rope for leeway and forgiveness. Canon really needs to get on the ball and COMPETE with the competition, and produce something that at the very least is on-par with what Sony Exmor sensors and Nikon DSLR's are offering. Remaining stuck at approximately 11.5 stops of maximum theoretical DR (read that as limited shadow recovery...a critical factor in photographing landscapes at sunrise or sunset) and increasing read noise with each successive generation of a camera is just plain and simply unacceptable, from an otherwise avid Canon customer's standpoint.
Remaining on this path will LITERALLY make me move my landscape photography to the Nikon D800e and a 14-24mm lens. It is certainly not something I want to do...I have nothing against Nikon, but I don't really like having to double my expenses and use two different products for the same general thing. I would much prefer to stick with Canon for 100% of my photography, but landscapes bleed extensive dynamic range, even with GND filters. Nikon and Sony have directly addressed this problem, and at a cheaper price point to boot...thats a very difficult thing to stick ones nose up at, especially when things seem to be moving in the opposite direction for your chosen, preferred brand.
So here is a heartfelt plea to Canon from a vested user: Please put some serious effort into addressing low ISO performance, and find some way to eliminate read noise. Please stop finding ways to "cheat" the system (i.e. using more translucent red and blue color filters in your bayer CFA to increase signal...thats just a copout, and you can do better! :mad
Some measurable, meaningful improvements in the categories of dynamic range and read noise are an essential requirement for my continued patronage of Canon. I'll probably always stick with this brand for my action work, I'm too thoroughly invested in Canon telephoto lenses, batteries, and accessory gear to switch, and high ISO performance doesn't seem to be a problem. But I can't limit the bounds of my photography and creativity on a matter of principle or the desire for convenience, and improvements to dynamic range and read noise were, ultimately...despite all the other shiny new features in the 5D III...my primary deciding factor regarding whether to buy one or not.
So please, stop the half measures and simple tricks to barely scrape by and maintain the status quo. Put some real, honest, dedicated effort and innovation behind your next sensors. Make some recognizable improvements (particularly, eliminate as much read noise as possible...fixed pattern noise visible in the low midtones or making shadows entirely unrecoverable is just no longer acceptable when its been demonstrated by the competition that FPN can be eliminated.) Give me a really good reason to keep talking up Canon as an excellent brand for any and every kind of photography, and stick with it myself for all of my own photography. And do it soon...I've waited three years for the 5D III, which is exciting in many respects...but in all honesty a let-down in terms of overall IQ, enough so that I've decided to hold off on purchasing the thing I've waited so long to buy. 
