There are also reasonably priced online custom matte-cutting places. Now that I need those links, I can't find them anymore. Sorry, but an online search should find them easily enough.
I bought and use a matte-cutter, am not a complete klutz, but am not sure it was worth it, having later found sources for custom mattes. Unless you do it often and a lot, you get rusty at using the equipment. Also, you have to enjoy the doing of it, not everyone does, and it does take up some time. I'd say, try a custom matte-cutting place, and if you're dis-satisfied, buy your own cutter. If you decide to buy your own matte cutter, like all tools, it rarely pays to buy a cheap one, you're not saving much in the long run.
Also, when you cut your own, you have to worry about keeping the right colours of matting material in inventory. Not a big deal, but one more thing to do and more stuff to store around the house.