So I was listening to the Save or Die podcast (http://saveordie.info/) episode 160: Start! Thief! in which they talk to Darrold Wagner: the guy who literally created the thief class for OD&D. Wow... that's living history! (I mean this in the best possible way.)
I recommend the full episode, but the Sparknotes is that the class was created organically, just through the course of play. It was originally intended as an NPC class, too. It was not - as I had mistakenly assumed - created as a way to emulate the archetypes in LOTR.
In my current OSR DnD game, I play a thief. Our homebrew rules don't do race-as-class, and my thief character is also a halfling. Playing a thief is a very particular experience. There's not a ton of glory... though there is occasionally a moment or two. The class has low hp, poor AC, and is pretty garbage in combat; going off solo to explore is not only deadly but disrupts the game as it forces the rest of the gang to wait out your little vanity episode; and, the expectation is that the thief is the poison-tester (hey thief, open the chest, open the door, etc etc). For these reasons, the class is well suited for a support player or a role-player, but not so much for a power gamer. One nice thing is that the thief does level up quickly. TBH, I think it takes a careful and conscientious DM to handle a thief in the party. Deadly traps will eventually take out the thief. Maybe that's not a problem though... it makes sense even. A cool death by swinging pendulum blades? Hey, you could do worse...
You know where a thief would really shine? A solo adventure! Man, the class seems to have almost been created for it.