Here's a scenario: You take notes as fast as possible during class. You try to study a few days later, only to realize that you can't read your chicken-scratch. Sound familiar?
If it does, I have a solution: Re-write your notes outside of class. This has a lot of benefits. First, it gives you permission to use shorthand that you might not use otherwise. It puts you in the position to be able to write faster and more sloppily than if you weren't going to re-write them.
Next, writing helps you to remember things. If you normally type your notes, chances are that the words your typing won't stick in your brain the way that they would if you were hand-writing them. When you type, yeah, you know what you're typing. But I never remember the things that I type. I always remember the things that I write with pen and paper.
When you re-write things at a later time, you can make your notes pretty and aesthetically pleasing. You can organize them differently than how you would organize things in the moment. When you start taking notes, sometimes you don't realize how involved they'll get. Before you know it, you're indented FIVE TIMES and writing in the middle of your paper. If you re-write them later, you'll already know how you need to organize your notes.
When your notes look good, you can very easily find what you need. Using highlighters and color-coding your work can make this even easier. These easy organizational tweaks can make studying easier and more effective. If you can't find what you're looking for, how do you expect to study?
All of this applies to notecards, too. Making flashcards can be a really awesome way to study. As a music major, even I've found a way to use flashcards. I write a key on one card, an articulation pattern on another, then a scale or pattern type on one last card. After I draw a card from each category, I just play what I'm given. You can easily apply this to any study or subject.
There are really no drawbacks to re-writing the notes you take in class!