I too was once a big cigar smoker, and kept may may boxes on hand at any give time in a number of humidors (I guess TAD is in my blood...).
The analogy I use, as imperfect as it may be, is that cigars are like the Whiskey of the tobacco world. And pipe tobacco is like the wine. Neither is better, but they are very different. As Roth said, cigars are much more "in your face". Pipe tobacco is far more sublte.
What makes the transition more challenging is that the implement itself - the pipe - really takes awhile to master. I had no idea, when first venturing into pipe smoking, just how long it takes to start getting the hang of it, learning how to keep the pipe from over-heating, sipping the tobacco smoke, keeping it lit, avoiding mouth-scortch and tongue bite, etc.
Not that I am an expert by any stretch, or that I have "mastered" anything, but now that I've got the hang of the pipe, in retrospect I find much more complexity and variety of flavors (not to mention textures and aromas) in pipe tobacco than I did in cigars. Add in the difference in mouth feel, draw, and flavoring of the near infinite variety of pipes out there, and it makes for a lifetime of journey.