Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
I haven't noticed a real performance difference from my 2010 11 inch ultimate to my 2011 i5, except on some things like Aperture when I was on vacation and looking at photos (but that may have just been my perception). But I mainly use it for word processing, web surfing, and other minor tasks that don't really tax the processor. I only upgraded because we needed another computer for another family member.

In fact, the most noticeable things for me are that the new one runs slightly warmer. The older ultimately was almost always cool -- except when flash was running. The newer one gets warm--not hot, but still annoying--a lot.

And I have a perception that the battery life is worse, but I have no empirical data to back this up, and I haven't used the latest software update to see if that makes a difference.
 
A lot will disagree or have different needs, but for me.....

My 11" MBA is mainly for a SECONDARY computer. I have a 2010 Ultimate, and it does everything I need it to do! No real need to upgrade in my situation. I wouldn't have bought it if it was my only computer. Love the battery life, portability, size, and weight. GREAT computer. I'd buy it again in a heartbeat. I sold my iPad 1 to get it, and I've never regretted it for a second.
 
I found that the difference in performance would be most prominent while fixing photos in Photoshop or Lightroom 3.

The 2011 model from my test was significantly speedier, but also significantly hotter than the 2010 model, not to mention battery dropped much more rapidly. It's very noticeable with the 13" models.

It's like a trade off between waiting 4 hours to finish an entire album, or 2 hours to finish the same album. In both cases, the MBA would run out of juice when it's finished.
 
cool, i might pick myself a cheap 10 model over a new 11 model. I like the air for the portability, and the built in SSD. but if its a minor performance difference (mainly just processing).

I think this was mentioned but not really into, how big is the performance difference when playing games? if any?

Depending on the game, the frame rates might be higher on the 2010 with its Nvidia 320M graphics.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.