I learned how to play on old non-heated Carom tables and re-learned the game on the Euro heated equipment. Forget about the heat for one second and consider that the tables play different in terms of angle of rebound and table speed, which is a result of the different rubber used for the newer tables. There are shots that are easier on the newer tables and more reliable, but again, I think it is more the rubber than the heat. The heat is there to aid in reducing the humidity in the cloth which is another key improvement, but from a consistency factor more than anything. As Bob said, in certain parts of the country it is not needed. Having played on newer equipment with the great rubber, if I had to go back to the old Brunswick tables I would probably quit playing the game.
As far as retrofitting Euro rubber on old tables, it is possible. It is however a great ordeal and usually, in my experience, it doesn't turn out very well. Rail height is important and the old tables are made for three-sided rubber which points down to the ball, so the tops of the rails (where the diamonds are) are typically higher than they are on newer tables. So when you put the new rubber on an old table, a new liner must be used, and that creates a gap between the top of the new rubber and the top of the rail. The cloth does cover the gap, but you can easily push the cloth down and when the ball is on the rail you have to elevate the cue moreso than on the newer tables. The only solution is to mill down the tops of the rails risking losing the diamonds...or of course you can just deal with the gap.