Might be related to the same issue described here:
http://forum.unity3d.com/threads/jittery-camera-movement.256420/ and

http://fogbugz.unity3d.com/default.asp?619093_dtpufuedu1bpuv84

The report mentions WebPlayer only but it's noticable on anything where the framerate isn't in the hundreds.

Unity 4.6 is coming out, I didn't see anything related to this issue. It is pretty disappointing, my game still runs worse on my HTC One M8 despite it being much more powerful than my Iphone 4s where it runs fine.

SLEDGEMAN, this did not work for me. Also tried to add some movement on a GUI.Button. This also stuttered, so it has nothing to do with Sprites. Just a framerate issue, vSync or something.

I found a solution that stops this hick-ups & stutters, on my project. The bad guy here is : BOX2D / Rigidbody2D. As i switch my whole project from Rigidbody2D to Rigidbody3D , no more hick-ups & stutters appears anymore. I have to say that physiX has much better performance than Box2D.
The Box2D integration isn´t implemented well, yet. Maybe in a distant future Unity will make it better. For now it is worse & really bad performance on old devices. PhysiX plays superb on old devices !

Hope this advice can help some of you. Cheers...

Have this issue on iOS devices when trying to make an endless runner.

An iPhone 5 tends to not be noticeable if at all, but when testing on an iPhone 4 with just a simple sprite that moves from right to left and resets, I get jitter as is scrolls across.

I enabled the internal profiler since I don't have access to Unity Pro and this caught my eye at the time of the stutter when testing on an iPhone 4. These are some of the stats for 3 consecutive frames from the internal profiler enabled in xCode.

=====
iPhone Unity internal profiler stats:
cpu-player> min: 2.6 max: 6.9 avg: 4.2
cpu-ogles-drv> min: 0.1 max: 2.0 avg: 0.3
cpu-present> min: 0.7 max: 5.3 avg: 1.5
frametime> min: 9.5 max: 21.6 avg: 16.6
player-detail> physx: 0.7 animation: 0.0 culling 0.0 skinning: 0.0 batching: 0.0 render: 1.6 fixed-update-count: 0 .. 1

=====
iPhone Unity internal profiler stats:
cpu-player> min: 2.3 max: 47.1 avg: 5.5
cpu-ogles-drv> min: 0.1 max: 0.2 avg: 0.2
cpu-present> min: 0.7 max: 6.5 avg: 1.5
frametime> min: 4.4 max: 54.7 avg: 18.0
player-detail> physx: 0.5 animation: 0.0 culling 0.0 skinning: 0.0 batching: 0.0 render: 3.2 fixed-update-count: 0 .. 2

=====
iPhone Unity internal profiler stats:
cpu-player> min: 3.0 max: 6.8 avg: 4.1
cpu-ogles-drv> min: 0.2 max: 0.4 avg: 0.2
cpu-present> min: 1.1 max: 6.4 avg: 1.6
frametime> min: 10.1 max: 23.5 avg: 16.4
player-detail> physx: 0.5 animation: 0.0 culling 0.0 skinning: 0.0 batching: 0.0 render: 1.9 fixed-update-count: 0 .. 1

Notice how CPU, frame time, and render all jump for 1 frame (the frame where a random jitter happens), and then goes back to normal.

Having these stutter issues on IPod 4th and 5th gen, when Iad Banners are running(native Unity adbannerview integration). Running fine whithout banners.
Checked on Latest Unity versions 4.5.1p3 and 4.5.1p4

I have 3x Android mobile devices. One dual-core other quad-core. On all of the three it comes up to this
annoying problem. Really sad !

Would like to know, if Unity3D Devs could tell a time frame when this would be fixed. I think for all users who have a paid version of Unity3D and earn money with their mobile-games work, they rely on a stable version of Unity3D. So if any U3D-Dev reads this, it would be nice to tell the users "when" this would be fixed (this year? next year ?) ...

DOnt know what next will I do, every single thing I put causes a massive spike.
Unity 4.x really is vulnerable in stuttering. my device is galaxy s2 and s3.

the problem I cannot solve is the spike on playing in an animtion on animator. and many more.

http://forum.unity3d.com/threads/unity-wazzup-our-game-is-stuttering-i-thought-your-software-is-good.253041/

Do anyone have the solution.... I've same problem on IOS 7 (particularly on retina display)

I am having this issue while testing a very simple game on my HTC One M8, latest Android build and using the latest Unity build. For me the issues don't appear on my IPhone 4s.

Please fix this asap :D