By now, you probably received the IBM selection package. It looks to me like not much has changed except the prices on some of the offerings and Aetna withdrew one of their Medicare Advantage offerings (PFFS). As an aside, I will speculate that they did not have a very good doctor network and the new regulations from the government to provide network specifics pushed them to shut it down.
I still don't think there is any "best choice". Each offering has advantages and disadvantages. The Medicare Advantage plans are as good as the doctors and hospitals they require you to use. If you want to go to an expert doctor or institution such as Sloan-Kettering you might not be able to do it. Make sure the plan gives you access to the doctors and hospitals you want to use.
The Aetna Integration Plan A is really tempting for those of us who use Original Medicare. It looks like a medigap insurance plan but at a fraction of the cost. It is NOT a medigap plan. Last year I went to their website to look at the detailed coverage and mapped it to a "popular" medigap plan to see how it compares (for example, details like skilled nursing coverage). The booklet you get from IBM does NOT provide sufficient information to let you do a comprehensive comparison. Since the Integration Plan A is not a medigap plan there is no governmental agency overseeing an appeals process. Again, I don't think that is a big deal. It is just part of doing a comparison.
All said, I personally was really tempted to sign up for the Aetna Integration Plan A. I decided not to do it when I looked at medicare.gov and got estimates from plan finder for my out of pocket costs on a non-IBM prescription drug plan. I estimate I would have to spend about $2000 more for my drugs with a non-IBM plan. Given that - I will take the bet (essentially a $2000 bet) that I will be healthy in 2011. (I lost that bet this year and reached the Out Of Pocket for the medical plan - $4000.) Still, I am staying with the IBM Medical/Prescription Drug Supplement plan. I know I need the drug coverage, I don't know if I will need the medical coverage, and I am an optimist.
I used myself as an example just to show the kind of work you have to do to pick the plan that is best for you. In the end it really is gambling. IBM is betting it can make money on you and you are betting you will have lower medical costs.