We ran an extended trial on Sonora plates some time ago, with about 5,000 plates going through.
We run a Heidelberg SM74 with the most common paper size being 650mm wide, which leaves 45mm of plate either side of most press sheets.
Due to this, the press operators found the emulsion, which couldn't be transferred to the paper in this area was building up on the rollers, resulting in them having to take rollers out of the press regularly and scrub off the buildup.
They also found that the rubber rings on the plate loaders were picking up ink from the plates as they were removed and transferring to the fresh plates. Where this occurred, the plates were failing to process, leaving spots of emulsion behind.
The only solution to this was to do a blanket wash and sheet the ink off the plates prior to unloading. As we run a lot of short run bookwork, with quick changeovers, this proved to be inefficient.
Following this trial, we reverted to using a standard wet process plate.
There is certainly a place for process free plates, but they don't suit all situations.