I take private lessons abt twice a month, and I have also found it beneficial for my progress. It also gives my instructor an opportunity to focus on me and pick up anything he may not spot during class. In addition, I get to focus on any of my personal deficiencies (i.e. timing, speed training) which we may not do in class.
Do I think private lessons are worth it? Well, it certainly depends on what you are looking to get out of it. For myself, it is really a chance for me to go deeper into the art, to learn more technical nuances, and also push my progress farther. Very few of my classmates take up privates, but they can still perform very well because they have been training longer than me or just as well. I also usually invite my classmates to attend private lessons with me but the cost of the fees is an issue, so I understand that people have to take that into consideration.
In regards as to whether beginners should take up private lessons, there's no righr or wrong answer. Personally, I wouldn't. I like training in classes because I get to interact with other students, observe other beginners and also learn from senior students who can give helpful advice since they have been in your shoes before. Also, while there's nothing wrong with learning privately with the instructor, you also want to get a chance to spar with students of your own level. I did start taking up private lessons considerately quick (less than a year since I started), but it was because I had to be comfortable with my instructor's teaching methods and I could also, more or less, discern what I needed to improve on.
Right now, I am quite happy with the current arrangement, and unless my income improves substantially, twice a month supplemented with class lessons is a good fit for my lifestyle. Don't forget you do want to have some time to train on your own so that you can assess your own progress.