In fact, I HATE the noise and it would be probable the only reason for me to spend that much money on a full frame. But I'm not convinced on the true advantage on a full frame here. At least not an advantage which is worth several thousands of dollars.

5D's don't cost several thousands of dollars though.  If I picked up a 5D for about �1000, then I should imagine a 5D body is available for under $2000 in the states.

There is absolutely no way that those images would be acceptable for stock (I can see the noise plain as day at the small size, at 100% it would be ridiculous).  There is noise, and then there is stock level noise.  Camera reviews address noise for the general public (and Rebel reviews are for DLSR noobs).  If there is any hint of noise the image wont be acceptable for stock though.

All the reviews of an XT show that there is an insignificant gain in the amount of noise from iso 100 to 200.  True, if you don't pixel peep.  Before I started stock shooting I kept my camera in 200 iso.  The pictures looked fine, even full sized.  Once I started going over them with a fine toothed comb the noise was everywhere.  At 100% the amount of increased noise is very significant.  Getting any images accepted even at iso 200 is a struggle and requires heavy PPing, even then no way for SS and IS.

The gains made in noise reduction just offset the losses due to pixel density, and noise reduction = overfiltered.

I highly, highly doubt that the new Rebel will be useful for stock in any ISO other than 100.

Also no matter how much reduction is done to the noise, you cannot escape the fact that higher pixel density = less dynamic range.  The white noise level is increased on the low end, to combat it black becomes black faster than it would on a chip with less pixel density.  There is no software workaround for this, it is an unavoidable fact of sensor technology.  The light collecting buckets can only hold so much, when white noise is increased the buckets hold less.  The only sensor that does not face this too much is the Fovean chip in Sigma cameras.  This is why pictures taken with good old 2 MP PnS cameras typically look better at normal viewing size than ones taken with todays 7+ MP ones, the high MP cameras have absolutely no dynamic range.

I highly, highly doubt that the new Rebel will be useful for stock in any ISO other than 100.

Well, maybe i'm doing something wrong, but my images shot with a Rebel XTi at ISO 400-800 get accepted all the time at IS and SS. I do sometimes use NeatImage to reduce noise in sky etc, but I'm not always locked into ISO 100 for stock.

Still better than the 17-85 though.  Of course the 17-55 IS is the best, but is it worth 5x as much as the 18-55 IS when you could get a 17-40L + a 50mm f/1.4 for less $$ than the 17-55 IS, both of which are FF lenses and have fantastic IQ.  Distortion , vignetting, and CA's can easily be corrected with software, resolution cannot be.

I wasn't remember the 17-40 who's a good choice. I heard many good things about it but I never try it.

Maybe I missed something (I'm not a wizard) What software do you use to correct vignetting?

The 5D produces better quality photos than a 1.6x crop camera.  The sensor is better, the colour reproduction is better. 

I don't think this is correct as a general statement. 5D is indeed better quality than 350D or 20D. However the quality comparisons with 40D that I've seen aren't any better for 5D - the quality is basically the same! Sometimes 40D is even better thanks to 14-bit processing...

Yes you get wide angle with 24mm lens, but on the other hand EF-S 10-22 is quite compact and light which you can never get on full-frame...

With the latest generation of cropped SLRs the advantages of full frame camera are much more doubtful for me than ever before...

The 5d has been around a few years.  I am sure the new version of the 5d will make the 40d look inferior again.  I can't see how you can get similar quality cramming pixels on to a small sensor.

If you look at the 1DS MarkIII results the new 5D will be as good or a new revelation. Add maybe a 16mpx sensor and there is it, I change my Nikon gears for Canon...If Nikon don't move until one year after the announcement and that's probably what is going to happen