Any one use Houdini's Compositing option? If so, how easy/hard or good/bad does it function?

How does it compare to other node based compositors or After Effects?

All the time. I use it for image processing and relatively simple compositing.
I find its strengths are: vop filters, ROPs (+ pre/post render scripts), distortion filters, colour correction and use of variables.
Its weaknesses are: tracking, keying, roto, graphics-card related flakyness, one docked viewer and abysmally poor (as in like a scripted prototype) performance, for both processing and interaction.
I find the strengths can mitigate some of the weaknesses if you use it primarily for batch processing sequences (on a render farm) and for simple comps where you may want to use custom tools and automations.
Overall I find that I get nicer comps out of COPs than nuke of DF… possibly because the awful performance forces me to keep things simple