Yes, Broweyes, it is useful...
Lets see here, which hardware are we talking about... are you using it for the Leap Pad, the one with the pen attached, or another hardware device, like the Turbo Twist Math, Spelling, Vocabulary, etc...
Last year for Christmas my MIL bought the DD a Leap Pad (one with the pen attached), and my son a Turbo Twist Math.
With the leftover money, we were able to buy a Leaplink, on clearance at Kmart for like $5 or $10.
When we opened the Leaplink, we found that we got 6 months of the website membership for FREe. We downloaded quite a bit of stuff. The Leappad we used for games for my DD. (They were called Echos' Jungle, and a maze game and stuff like that). We also got a stiff holder for the papers we printed out.
My DD was (and still is ) a non reader. The things were easier Pre K, Kindergarten stuff.
But we used it heavily for the Turbo Twist. My son complained that the current level in the machine was too easy, so we would download different grade levels for him. He did say all the math was too easy no matter what level we downloaded. We got up to 6th grade (he was in 1st at the time) then he was finally challenged.
With the Leap Pad 6 months free, you do get Leap Pond magazine. You download the sounds off the website, and use it for the current volume. We got 7 of these, and both my kids now 5, and soon to be 8 enjoy them. We just renewed because they do enjoy the magazines, and with renewal we got another cartridge for free.
Also in the Leap Link there was a free cartridge in the box. I feel that we have gotten a deal because the Leap link was on clearance, the kids have enjoyed the downloads, and the magazines are good and durable (just like the books you buy).
We have never bought any extra books because of the magazine issues. That being said, we don't use the Leap Pad for a "learn to read" tool, but more of games, memory, and brain twisters.