Well, I restored back to stock 4.3.3 just to see what it's like again after using the aforementioned "tweak" for over a week now.
Suffice to say, it's hell. Choppy opening animations, stuttering midway through launches (Messages, Phone, Settings), and just generally sluggish navigation.
My iPhone 4 is now in the process of being jailbroken again, because there's no way I can use stock 4.3.3 again ...
Ok, I tried going ack to 4.3.3 with jailbreaking and using the "tweak" then compare it to my wife's 4.2.1 - the results are as follows:
the removal of the two lines does make a difference as everyone noted here
the addition of the old lines do not add any value, and apps still don't load while the animation runs, you can test it youselves if you want.
if you download an app from the app-store without the need to enter the password again (meaning you download twice in less than 15 mins), the zooming out off the app store and then going to the page where the app icon will sit, stutters lIke hell !!! On the 4.2.1 if there are only 3 rows of icons it almost does not stutter.
when shooting a video with the camera app and zooming out of it to a page with more than one line of icons, stutters like hell !!! On the 4.2.1 much less !
on the mobile phone app when you call a person from the recents list the zooming out feels less smooth in many out of the calls I performed. On 4.2.1 - almost unnoticeable.
4.2.1 is not stutter free but you can feel that even with the "addition" of the tweak in 4.3.3, 4.2.1 feels much less heavy on the iPhone 4 platform.
Don't forget that on 4.2.1, applications DID launch during animations and it didn't feel that heavy.
I really don't know what apple have done here with 4.3.x but it might be just the fine-tuning done for an A5 chip instead of the A4.
If you ask me, I still don't know which one I prefer. I'm still changing my mind everyday, but at least now I know all the pros and cons of each one.
Jonathan.