With V4.1 I had a couple of grips:

1. It seemed to exhibit a long frame stutter at a fixed interval of about 1 second. This is despite being able to maintain over 30fps for a smooth 30fps locked at 30hz. All the hallmarks of a long frame stutters.

2. Really blurred textures in some scenarios.

Both of these issues are highly reminiscent of the bad old days with FSX

 

So the question is despite everything else is there any performance improvement in V4.2?

 

Has anyone made an objective comparison and measured any performance improvement.

I know that DL is said to be improved but I am talking about performance where lighting setting

are all disabled. Raw FPS increases and improved FPS stability and improved texture loading.

Perhaps Rob A. can comment or another reliable source.

 

I noticed also something about improved SLI support. Any comments from duel GPU

users would be much appreciated to to help me to decide if a second GPU is worth it.

I would say it is far too early to expect people have comparisons already posted. Honestly, I don't know of anyone who has successfully upgraded to 4.2 yet. I would expect comparisons to be out in the next couple weeks, but until all third party add-ons update to 4.2, I don't see how there could be valid comparisons made yet. You may be waiting a while for a good answer. 

Beta tester like Rob A. would I believe be in a position to offer some insight here. I would interpret silence (which is what I expect) to be an answer in the negative.