I got all the way through Dead Space with mouse and keyboard and had no issues at all. One mistake I made was selling my default weapon(plasma cutter) at the first chance I got and never used it again till near the end. It's really worth upgrading as soon as you can.
I liked Dead Space, but wasn't blown away by it. Mute main character, missions and story are totally contrived. I didn't like the credit collecting and use of shops on a derelict mining ship. But it's got good atmosphere, looks great, and has some pantpooping bits. Certainly worth a blast on the cheap.