What I like about obsidian - and in the end why I went for that, despite the price (though I got a good deal on it, as you saw), is its intrinsic qualities. I've slowly been working more with black stones. I used to find them too heavy, though I always used to carry a medium-sized hematite around with me for grounding and to ward off the negativity that surrounded me in the places I worked.
But obsidian I only discovered a few months ago. There was a sale of stone hearts going on in some online shop, and one of them was obsidian, so I bought it. I haven't really worked with it actively, but it's beautiful, and I love having it about. I feel solid and anchored when I see it, but at the same time, I feel like there's a whole mysterious world in there to discover. It's a bit like Alice's hole in the ground...
The black obsidian mirror gave me a powerful jolt when I unwrapped it. I was awestruck by its simple beauty, but I was also mesmerised. I used to have an old fear of black abysses - whenever I went through a bad time, I would see a huge black hole trying to suck me in, and I was terrified. After a shamanic workshop during which I journeyed into the abyss and had some powerful, frightening but ultimately healing experiences, this fear has left me, but the fascination hasn't. I feel like it's an adventure...
I read somewhere that obsidian is good for creativity for those reasons - being both grounding and fascinating - it brings visions and draws you into a path of discovery - which is of course invaluable for creators. I am about to start a new book, once I've finished my contract, so I think my obsidian mirror is also something I have at the back of my mind as a kind of pathway for me. In the past, dreams and visions have inspired some of my writing, so I am wondering if scrying might not? It's simple presence near my desk (my altar and my workplace are both in my sitting room) is also inspiring.