A table is absolutely worth it. IF...
You are dedicated enough to be able to shoot alone on it on a regular basis. You aren't always going to have buddies over to play with, and the truth is, pool is not a game for 1 person - so you will be eager to play people in pool halls more so than playing on your own table.
What having your own table does it, it allows you to learn things you will never learn at a pool hall due to the hundreds of distractions. You can sit at your table, and drill a particular shot, at your convenience, in peace and quiet, and really dig in an analyze what the balls are doing. No one watching, no one bugging you. No noise, no nothing. Just you and the equipment.
Also, a pool table at your home will often be better equipment than a pool hall. I have a GCIII, perfectly leveled, with nice new simonis. I could play on this cloth for a year and not put the same wear on it that a pool hall table will incur in a couple of weeks. New balls make a huge difference too. pool hall balls have the 1-9 worn out more than the rest of them, that and the worn out racks makes getting perfect racks impossible. I rack 9ball, it racks perfect, no gaps, no spaces. perfect. No sardo needed. I make the wingball nearly ALL the time. Consistant conditions allows a person to figure things out faster. You can tell the difference between one thing vs. the next because the balls, cloth and table play the same way. You eliminate variables. How can you really break down the details of your break when a crappy pool hall table with the spot worn down to the slate doesn't allow you to break a rack the same way?
You can mark your table with those little stickers and place balls exactly in the same spots every single time. It is a hassle to do this at a pool hall, and sometimes not doable. It was only until I got a pool table that I truly learned exactly how various tip positions of english effect cue ball path off the rail. That is because on any given shot I set up, I am able to place object ball and cue ball in EXACTLY the same spot using those stickers that reinforce the holes on paper sheets for binders. When you do this OVER and OVER it burns into your brain, whereas at a pool hall...it takes many more times repetition for your brain to start "seeing patterns" and memorizing paths etc... If you can't recreate the same shot over and over, you will never learn or it will take much longer. Placing the object ball or the cue ball just a few degrees off, even if they look about in the same position changes the angle at which the cue ball will leave the object ball and where it will hit the rail, which all changes where the cue ball will go. It makes it so much harder to gauge what you're doing.
Another thing is - quiet. The first thing I noticed is that pool tables make noise when you play. In a perfectly quiet home, you can hear the ball roll on the cloth, you can hear the impact of the balls into the cushions, even on soft shots. This feedback is helpful. You hear everything and I believe this helps learn feel and touch a little bit better.
You can do various drills, you can do so in comfort. In your boxers, whatever. Having a table keeps you in stroke. Your arm is kept in tune because you have access to hitting balls any time you want. If you're really extreme (or smart) you'll get yourself a video camera and tape yourself shooting. At first, you'll be thinking about the camera..but after time, you won't even notice and your true stroke and play will come out. You can review the tape and see how you play. That is HUGE. Nothing is better than real feedback. You'll be surprised to see how well you do somethings and disgusted at how bad you do others. I shoot some shots like a pro, and others like an idiot. The tape doesn't lie. It will help your stroke mechanics more than you can imagine. A pool table in your home, for many reasons, allows you to experiment in ways that you cannot or would not try in a pool hall for any number of reasons. One of the biggest ways to learn is experimentations. That's because to improve, you have to add new things to your game. If you just shoot what you know, you'll never improve.
I could go on for hours on all the little things you can accomplish with a table of your own.
A good pool table will spoil you. Nice rails, nice cushions, nice cloth, level..will make even decent pool hall tables seem like junk - but overall, it will help your game.
If you are not dedicated enough to ever hit balls or analyze your game or try new things, then the table will do nothing for you.