I had been tuning my drums by ear and was frustrated by the sound. Then I realized that, as a long-time guitarist, I am perfectly capable of tuning my guitar by ear, but having a tuner makes things WAY easier and quicker. Good guitar tuners cost in this vicinity--the price is fair for a drum tuner.
It is quite easy to use. Don't be dissuaded by comments by others that say it's hard to use--I suspect they don't have much experience with electronic tuners in general. You can use this tuner simply by turning it on and hitting your drum around the lugs. If you want to get more in depth, you can read the manual and learn more of the functions. I found the filter function particularly useful, as well as the chart (available on their website) of recommended lug frequencies for tuning your drums to different notes.
I was pretty close by ear on the batter sides, but this helped me make sure the lugs were the same tensions, and it helped me a lot with the resonant heads.