iMac and MacMini are completely useless for dev or UX.
I've had issues with using Mac laptops for design and dev work, as well…my Sandy Bridge Air and my MacBook Pro (non-SB) are insufficient. I'm easily 3x more productive on my beloved MacPro tower at work, despite its many flaws and tremendous cost.
The Mac Pro Might Not Be Around Much Longer
All the attention is on laptops.