I've just renewed a PPL/IR after a four year gap with no instrument flying. I used my PC and a flight sim to prepare for it. In my case it was an old copy of ASA's On Top, which is designed for the purpose (more recent versions still available).
What I found good was the ability to closely mirror the setup of the aircraft I was planning to do the test in (PA28 with HSI), and the airfield I was using. I wasn't too concerned about the exact handling - I was using a joystick not a yoke, no rudder pedals. The sim is actually more difficult to fly than the real thing - much less stable and more difficult to trim accurately (may be my joystick) - but that actually helps improve scan.
It didn't exactly mirror real world conditions on the instruments - the ADF tended to point at the beacon, rather than flicker +/- 10 degrees as Cambridge's does in reality, for example, but it was excellent in being able to practice a route, holds, build situational awareness etc, and flying the route in a variety of winds. You don't get Air Traffic talking to you either of course.
Highly recommended.
Paul