Ableton's Complex warping algorithm, which is in the Standard and Suite versions, does indeed have comprehensive warping options. However with SONAR, Melodyne does an excellent job and the integration with SONAR via ARA is a plus. SONAR takes a more a la carte approach than many other programs, so it's not surprising that SONAR's ongoing partnership with Celemony is advancing SONAR's warp capabilities; there's no need for Cakewalk to re-invent the wheel, and people who don't need advanced warping don't have to pay for having it incorporated in the program. (Of course the downside of Live's Complex algorithm, or any stretch algorithm that maintains pitch while changing length, is artifacts; this is why many people use Live's re-pitch mode, even though pitch and time then become interdependent.)
The biggest problem with most warping is that although you can take something played freely and conform it to a tempo, you can't conform a tempo to something played freely except in SONAR and Studio One. This is because both of them have made it a priority to integrate ARA.
As to "clumsy and unintuitive," I'd hang that label on AudioSnap but not the Loop Construction window. If you want a simple solution to stretch something into a file capable of being looped, slip+stretch with DSP or using Melodyne are fast and efficient. However, the Loop Constructor has very deep and capable functionality. The price of that depth is it's necessary to study how it works. Once you do, it's pretty obvious. It certainly isn't any more complex that the way you create stretchable, real-time key-mappable loops in Sony Acid or with the Apple Loops SDK, and the Loop Construction window can also do Ableton's re-pitch functionality.