If you recently jailbroke 2.1, press and hold an icon on the home screen to get your icons wiggling. Now, are the icons smooth around the edges or do you see sharp pixelated edges as they move? It looks like like the anti-aliasing has been turned off by the jailbreak. Also, opening Apps took one second longer to open than without the jailbreak. I was just talking to a friend tonight and he has the same problem. I restored and refused to jailbreak 2.1 and my icons wiggle like normal again. Nice smooth edges around the icons.
Has anyone else seen this? If you can, take a screenshot of it because during my restore, I lost the screenshot I took. (Yes, I should have saved it, but I didn't). To take a screenshot while your icons are wiggling, you have to hold home down and while holding home, you must hold an icon until they start wiggling. Keep holding home and press the power button to take the screenshot. If you don't hold home the entire time while you do this, the second you press the home button to take the screenshot, the icons stop wiggling thus making it take a normal screenshot (no wiggles).
It's late and I'm tired... I hope all of this made sense.
Recap: Do your icons have aliased/pixelated/jagged edges while they wiggle or are they smooth as they've always been?
Edit: Here are screenshots I just took. I just installed WinterBoard on my jailbroken iPod touch. WinterBoard is definitely the problem. If you have WinterBoard installed on 2.1, you probably have jaggies.
Before:

After:

Look at Safari, Mail and Photos and you'll see the stepping effect I was talking about. It's smooth on "Before" and "Jagged" on After. Please view the images full size.
Has anyone else seen this? If you can, take a screenshot of it because during my restore, I lost the screenshot I took. (Yes, I should have saved it, but I didn't). To take a screenshot while your icons are wiggling, you have to hold home down and while holding home, you must hold an icon until they start wiggling. Keep holding home and press the power button to take the screenshot. If you don't hold home the entire time while you do this, the second you press the home button to take the screenshot, the icons stop wiggling thus making it take a normal screenshot (no wiggles).
It's late and I'm tired... I hope all of this made sense.
Recap: Do your icons have aliased/pixelated/jagged edges while they wiggle or are they smooth as they've always been?
Edit: Here are screenshots I just took. I just installed WinterBoard on my jailbroken iPod touch. WinterBoard is definitely the problem. If you have WinterBoard installed on 2.1, you probably have jaggies.
Before:

After:

Look at Safari, Mail and Photos and you'll see the stepping effect I was talking about. It's smooth on "Before" and "Jagged" on After. Please view the images full size.