Well for me and I hope Karl too the faders work very well no jerkiness in X2. If they are working well in other DAWs then its likely your unit is working well. 
 
Its up to CW to bring full support to the MC. When this will happen I don't know. It is not as much of a problem for me because I don't use the MC to control the ProChannel or VSTs. 
 
What I do miss is the F buttons are not as useful as they used to be.  A lot of options that they used to control are gone. 

Thank you John! You are right. I 'll be waiting for a .dll update. I also think, that the F buttons do not provide the sufficient options.
All the Best,
Adam

Adam please forgive me. I just noticed you are new. Please take this belated welcome as you are really welcome to this forum. 
 
You have a very nice style that I for one appreciate. 

amax55
Thank you John! You are right. I 'll be waiting for a .dll update. I also think, that the F buttons do not provide the sufficient options.
All the Best,
Adam

Hi Adam - ref the F buttons. You should be able to assign just about any function to those. As long as it is available in the ACT function list (even though it doesn't use ACT as such).
 
Open up the Mackie properties page from the Utilities menu and change them from there. You can set up several different presets as well and load them as needed.
 
HTH

Thank you John for a very nice, warm reception. I did not expect it. Thank you!  Back to my problem with MCU PRO... Today is the last day I can return it to seller. Most of facts show me, the device is not defective, but I do not know, what to do... Keep it and wait "nobody knows how long" for SONAR's dll update or return it, to wait for an update and then buy it again (it could be an year or two of waiting for that .dll!). Hmm...
Best,
Adam

And Karl - thank you for an info about F-buttons. I know about assigning these buttons to various functions by presets, but, in my opinion, it too bad we can not to assign the F-buttons to remaining possible functions in menu.
Best,
Adam

I would keep it. But then I have had mine for a very long time. 

amax55
John, how are you?
I just tried another DAW applications with my MCU PRO. After testing my SONAR X2 (faders are jerky), next MOTU Digital Performer 8 (faders goes smooth up, but jerky down) and finally MAGIX Samplitude Pro - here faders works, say, good in both directions. And what should I do? I planned return the unit (as defective) to the seller, but in actual situation? I do not know... I do not want to work with Samplitude (although it looks enough attractive), beacuse I use SONAR for few years.. Do you think, this mysterious .dll file in a new version could help me with these jerky faders? (and these not working buttons) in MCU PRO?
Best,
Adam

Samplitude Pro X has the best Mackie MCU and XT that I've tried.  You can pretty much program any button to any function.  However, some of the LED implementations are a bit wonky.  That could be because I haven't learned how to set the button up properly.  

Reaper's MCU drivers have been written by users.  One of them has a great feature set but the author doesn't own an XT so full implementation of that is lacking.
 
With the exception of the ProChannel, SONAR's MCU implementation is very useable but I wish it was more like Samplitude.

Hi Adam and a "welcome to the forum and to using Sonar!  Both John and I joined about the same time in 2003 although he has a few more posts (about 23,800) and I feel humble.  Anyway, welcome to Cakewalk. 

Thank you 'Mod Bod' and 'FCCfirstclass' for your posts! In fact, Samplitude Pro X looks very nice and works good, I think. But I am more familiar with Sonar... I hope, Cakewalk will realease a proper .dll in near future. Thank you for warm reception in the Very Nice Forum!
Best,
Adam