In addition to 20% off upgrades to CS5.5 for everyone through the end of 2011, Adobe's offer of 50% off Adobe CS5.5 Production Premium or Premiere Pro for Apple Final Cut Pro or Avid Media Composer customers expires October 31st. As I mentioned when the deal went live, here's the coupon code, and some more details as well as a video about the discount:
Apple Final Cut Pro and Avid Media Composer customers can receive a savings of 50% off the full version of Adobe® Creative Suite® 5.5 Production Premium (Mac OS or Windows®) or Adobe Premiere® Pro CS5.5 software purchased through the Adobe Store. Adobe customers who own suite editions or individual products that qualify for upgrade pricing for Production Premium are also eligible to receive the same price (50% off the full version of Production Premium). When purchasing through the online Adobe Store, you must enter offer code SWITCH in the shopping cart before checking out when prompted to do so.
Adobe has also launched a dedicated website for switchers, which highlights such issues as being able to use all of Final Cut Pro's keyboard shortcuts within Premiere (which I've covered in the past).
Link: Adobe 50% Off Offer (use the code SWITCH)