They very much are, and have been, for awhile.
They left Photo CS 5.5 users twisting in the wind, recommending customers pay to upgrade their one-year-old software to CS 6.
I don't know if it was the external pressure or a slow in-house process, but it took them a month to release a fix for CS 5.5 users: http://www.adobe.com/support/security/bulletins/apsb12-11.ht...
Why do I find that hard to believe. Oh right, because I've launched and used Adobe software in my life.
You will certainly not notice any improvement in their "creative" apps.
But these do not really form a part of most people's "internet attack surface". The priorities are Reader and Flash. Perhaps AIR.
Adobe Reader X is a lot more secure than Reader 9 was. The bugs are still there - many Reader 9 bugs affect X. However, exploitation is much harder, and I haven't seen anyone get reliable code execution in X yet.
They are supposed to be working hard on Flash too, although I haven't looked at that recently. I remain unconvinced that Flash is actually fixable, but perhaps they could win with strong enough sandboxing and exploit mitigation...