Possibly my stupidest and most frustrating hobby, but still probably the one that I've put the most time and brainpower into.
For me, a lot of the fun comes from being in a space and having complete freedom to roam, open every door or climb any ledge. Natural weathering is also very beautiful in it's own way, like in romantic paintings.
Research can also be interesting sometimes, digging through obscure websites, archives, documents, images.
On the flipside, you can easily waste hours looking for something, heading over, and finding empty and burnt down corridors of graffiti and crackheads, or it'll already be demolished.
I managed to completely burn myself out on this hobby for a couple years because 99% of effort ends up being a waste of time, but I'm starting to get back into it because of one of my friends.
Also, this field seems to have become quite popular among the NORMALS (back when I first started getting into this, no one called it """urbex"""), which is both good and bad: good because the oldheads who hide away all their locations in secret invite forums or whatever get BTFO by the sheer onslaught of people crowdsourcing information, bad because there's more people which is always more miserable.

(For illustrative purposes, a little family house that I visited yesterday)
Anyway, does anyone else here do this? If so, did you see anything cool, or was it disappointing?