Paper plates work well for us in most situations. We use a mitsubishi tdp-459 II and do single and 2 color on offset. They work well for basic ncr forms, letterhead, and envelopes. Our biggest issue with them is that halftones tend to wear out early and can be pretty noticeable if there's a gray box going across the sheet because it usually doesn't wear down evenly. We use metal plates for those jobs. If there's a photo it doesn't seem to be as noticeable though. They're supposed to last 5,000 impressions but have lasted 8k-10k on some press runs if it's just line art.
There is a chemical we have to add to the fountain solution for the plates to work, slm-oa2. Without that ink will build up on the plate, usually on the gripper edges on the corners. We also use a webril wipe to wet the plate with the fountain solution to give it a head start before starting the press up. The image is very sensitive and will wear off if just about any other chemical touches it.
