For university mathematics, the TI-89 is highly recommended due to its advanced capabilities as a Computer Algebra System, allowing for symbolic manipulation of algebra and calculus problems. However, it requires a learning curve and discipline to use effectively, as it can lead to over-reliance on the device. The TI-83 Plus Silver Edition is also a popular choice, offering good value for various math and science courses. Some users find the TI-86 to be the most effective for general purposes, while others criticize the TI series for its complexity and the need for familiarity with the manual. Ultimately, the choice of calculator depends on individual needs and the specific requirements of the courses.