Definitely wouldn't buy a cat - they just turn up here and move in.
As for all the stuff about a serene presence on the desk... No, a cat will kick every writing implement off the desk, chew on random pieces of paper or tug on the mouse to see what happens. The small black one we call Squeak knows she can get attention by standing between me and the screen with her tail shoved up my nose, and recently helped out with editing-at-source by removing the K and L keys from my keyboard (now repaired!). Piper (6.4kg) is not a lap cat, unless I am sitting outside with a laptop, at which point he is a laptop cat, which makes typing difficult. Oatmeal (7kg) is a dedicated lap cat and waits until I am on the sofa with the laptop when he eases his way in and tries to push the machine off my knees.
In fact, out of four cats, only one doesn't take any active part in the writing process.
