"Propress" was pioneered by Statler-Viega. I have been using it (allowing it to be used) on my jobs for about 12 years now. No problems unless you forget to use the tool on it. (it can sometimes hold to about 40 to 60 psi before blowing apart if not pressed).
Many manufacturers now make the fittings. Tools are available in corded and battery versions. Pay attention to jaw sizes supported when purchasing one.
1. Some tools have a limited number of cycles before they have to be factory reconditioned. Be careful buying used.
2. Due to the popularity of this in the commercial market, used tools are hard to come by. New tools are very expensive so a lot of fittings must be pressed to justify the cost.
3. Once you press, there is no "unpressing". The fittings cannot be reused.
4. Fittings and valves are more expensive.
5. Need room to manuver tool. Preplanning a must.
1. Great for retrofit. Pipe doesn't required intensive cleaning or need to be dry.
2. Labor savings. - however I question the savings on 1/2 and 3/4" lines.
This technology has been used in Europe many years before the U.S. There have been other systems that use Schedule 5 Stainless prior to this.
You will be seeing a black iron version coming out in the near future.