Wow, I was thinking the same exact "godsend" too and turns out some other reviewer already said so. Very very helpful to assist deployment and pick modules to use. I personally made a couple of command-line scripts like pm-in-core or core-since-when to save some typing.
It does one thing, and it does it very well. More important is the fact that this one thing is really really useful and would, without this module, be really really tedious. I use "corelist" very frequently and every time I feel like I just saved fifteen minutes of searching.