For best results you should get some anti-backlash nuts for your lead screws, or even some inexpensive rolled thread type ballscrews might serve.
The trick to getting good finish and tool life is to "climb mill" as we call it. This is the method when the cutter tends to pull itself along the work, which could cause a lot of problems if you have a lot of backlash in your screw/nut. This is why ballscrews are preferred.
Another nice thing about climb milling is that you don't need a lot of power in your servo or stepper drives, because the cutter tends to pull itself along, so then the servo/stepper acts more like a motion regulator, rather than a brute force applicator.
Precision ballscrews would be highly recommended if you are attempting to produce holes on precision spacing.
Don't forget to take a look at the method that is used to mount the ballscrew to the table. It should be using ball bearings for thrust take-up, not sleeve bushings. This will eliminate one more source of backlash.