As you go higher in stakes they become more important, however at the micro-low stakes I wouldn't even bother buying one since its not too valuable. If your more serious and are playing mid stakes+ I would recommend getting one. Many sites allow you to have a free trial of one so check those out,.
Our extensive research disagrees with you. The HUD is most valuable at the lowest stakes where you're playing against massive fields of different opponents. The higher the stakes, the smaller the field of opponents, the less you need to use a HUD because you will tend to remember more about your opponents.
A HUD is a productivity tool, it is designed to help you remember who your opponents are and make the game more similar to the reads you get while playing live. In a live game your brain remembers faces and playing styles, you take these playing styles in your head and naturally create what we call an "Opponent Profile" to help you estimate your opponent's ranges and expected actions. Online the human brain doesn't work that way, its not easy to reproduce this natural occurrence because we do not have faces to remember, the human brain is not "programed" to do this for screen names. So we incorporated the same concepts behind baseball's stats into the
online poker HUD to reproduce how the brain works. The stats alone tell you nothing important enough, but if you take the multitude of stats together it helps you recreate that opponent profile in your head based on past observations. In the end the HUD does not make you a better player - it makes you a more productive player that can remember past situations better which in turn helps you create that opponent profile faster. Thats why most multitablers tend to use HUDs.
PS: We have a thread here in this forum if the OP has any questions specific to PokerTracker, as previously mentioned we provide a free 30 day trial + a 14 day money back guarantee.