All methods of "no prep" or "minimal prep" veneers have risks involved. If porcelain is thin, fracture incidence is more common. In an effort to NOT prep teeth, the results are often too big or bulky. Depending on where the starting point is, prepping teeth may not be avoidable to get the desired result.
No prep veneers are still permanent and pain levels are still about the same as prep veneers. If a person wants no prep veneers removed they must be cut off and the removal damages the enamel, which is irreversible. Reports of pain from traditional veneers is normally due to the inexperience of the clinician and not due to the material. I routinely have patients report no discomfort (of any sort) during the entire process.
No prep veneers are marketed to unskilled or untrained dentists as an easy way to improve a smile. However, cosmetic training is still needed to avoid the letdown associated with results that don't meet up as intended. Skilled dentists can and do offer this service, so homework on the dentist providing the service should still be done.
20% of my smile makeovers are simply redoing no prep veneers.