I think I first noticed this in SONAR X2, but didn't have time to investigate further.  I did some testing today and created this short video to show the effects.   Basically I go from ~55% CPU to ~90% CPU when aim assist is on.  A secondary find is by minimizing SONAR so I only see my desktop CPU loading drops again a significant amount (probably expected).   I initially thought it must by video card related as I'm using 3 monitors, 2 of which are the same signal on an active splitter, so I can have a monitor feed in my drum room.  After reducing my video down to low resolution, 1 monitor and using the VGA out instead of HDMI, there was no noticeable difference. 
 

This thread (already confirmed as I stated in your last thread)... Still no harm in another post I suppose esp as it has a video...
 
http://forum.cakewalk.com/sonar-X3d-now-time-playhead-Lag-when-moving-the-mouse-cursor-on-playback-m2952126-p3.aspx
 
Thanks...

Sorry,   I thought you were talking to the OP and didn't check into your link.  Moderators feel free to delete or move this. 

No I think the thread is valid. Maybe you should report this to cakewalk problem reporter as I'm not sure we covered every angle (we repro'd it in other ways), point them to your vid I suggest and this thread I suggest and let us know what they say.
http://www.cakewalk.com/support/contact/problemreport.aspx
 
Could you give us an issue number?
Thanks...
 

CWBRN-24525 - Report Details

Product: SONAR Producer
Version: X3a
Status: New
Summary: Aim Assist causes significant additional CPU loading
Description: 1. Open SONAR
2. Create a new project using the template "24 Track Audio"
3. "Collapse" the Console, "Inspector", and "Browser"
4. Open Windows "Task Manager" and view "CPU Usage" in the "Performance" tab.
5. Move mouse cursor into the track viewing area with the "Aim Assist" enabled.
 
Expected Results: CPU usage probably shouldn't jump to such extreme amounts while moving the "Aim Assist" line. On my PC, CPU usage moves from 2% with
Actual Results: On my PC, CPU usage moves from 2% with "Aim Assist" stationary, up to 50% when moving the "Aim Assist" line. If I have a real project with audio tracks, etc. I go from ~50% to 100% CPU usage and get increased audio crackling.
Provided Specs: Windows 7 Professional (Service Pack 1) 64-bit, 6.1, build: 7601 (x64) HP Compaq dc7800 Convertible Minitower, Hewlett-Packard. CPU: GenuineIntel Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz. RAM:4015 MB total. NVIDIA Geforce 210
Audio 1: Focusrite
Audio 2: Saffire Pro 40
Driver Mode: ASIO
Operating System: Windows 7 64-bit
Reproducibility: Reproducible

Report Submitted:

I also sent them a link to the video and this thread.
 

While submitting the report, I did notice the CPU loading appears to be affected by the amount of visible area of the track view.  This is why I suggested step 3 "Collapse" the Console, "Inspector", and "Browser" in the report as the effect is more apparent.

That other thread was pretty long though, and not sure if the Aim Assist was included with any report (I never chimed in until the end of it). Thank you for taking the time to submit this.

Ditto. Thanks...!

I think this should be resolved now in X3E if you wouldn't mind checking?
 
Thanks...

In case the OP doesn't chime in, I have verified this resolved in X3e.