I had a hard time with them (RS-SPL and AVIA). I wasn't sure what I was looking for. I haven't had the time to post an official thread yet:
The way I see it, if everyone says to get the disk, get it. Learn it after you buy it. There are enough people on here to eventually break through the coarse layer of skin around my skull that seems to inhibit me from fully grasping the HT concept. If they can teach me, they can teach anyone.
If the disk and meter seem like they are too much for you to spend, then most likely they are. If you can afford to spend $50 on something that you'll never really need, go for it. The worst case scenerio is, you realize you are too lazy to really care. The way I see it, save your $50 when looking for a wedding ring or baby toys. It's not like they really get used anyways. At least with the disk and meter, your wife can't complain because you're always out. You'll be too busy moving your speakers around for a couple of weeks to actually go anywhere! Besides, you can always measure the range of your wife's/girlfriend's voice. What could be more fun than that?