My "home" pool hall has one table with shimmed pockets and nine tables with buckets. As one of the higher skill level regulars there, I get asked this question a lot, and I think the answer varies depending on the person asking.
If the person is a new player or a player with poor fundamentals, there isn't much value in them trying to play on the shimmed table since it will just frustrate them.
If the person is a player that understands the game fairly well (knows multiple position routes, common patterns, etc.) and has decent fundamentals but has trouble making shots, I think that the shimmed table is a good table to practice on, but they should be alternating between that table and the bucket tables so that they don't get too caught up with making the ball and forget to develop their position play.
If the person is a banger that can fire balls in from anywhere but doesn't play position well, I tell them to practice on the buckets until they can run out a rack or two every night then try out what they've learned on the shimmed table.
If I'm talking to someone that occasionally runs a rack of 9-ball on the shimmed table, I tell them they are ready to learn one pocket. :wink:
If they string together racks on the shimmed table, they are out of my league and shouldn't be asking me questions.