Background: The room is Drexeline Billiards in Philly. It is a players room through and through. The tables are all GC4's, bought brand new in 2001 or 2002. The owner is a top player, and puts the best equipment, Simonis, centennial balls, etc, and replaces the cloth every 6 months.
A ton of the players play one pocket, and a 2 of the tables were always triple shimmed to accommodate them. About 4 years ago, the owner gave the one hole players a treat, by getting rid of the shims, and having 4 of the tables made with small pockets by extending the rails. I came the day after the cushions were changed, and the owner was very proud and said diamond cushions were installed. I believe the cheaper ones, not the Artemis, because the nose looks like a normal radius, but I never asked him.
Those 4 tables when the cushion was brand new 4 years ago react noticeably faster than the rest of the tables in the room. Fast forward to the present, with all tables getting new cloth every 6 months, and those 4 tables still react noticeably faster off of the rail.
As a side note, the rest of the tables (there are 18 GC4's), all play great. The cushions have held up great in 18 years.
Now, the 4 tables with the diamond cushions don't play bad, but they play noticeably different. IMO, the standard super speed cushion plays better. Most of the other players also think the same in that room. Conversely, there are also a few players that like the faster cushions better.