I am not entirely sure how big the GR reviewers hands are - perhaps this device is designed for kid hands like the pad on the GBA...but I have got to assume that there are kids who will buy this, use it and get it to work no matter what.
The situation with the stylus sounds more negative. If you can't simply strum as the game was intended, then there is "faulty hardware" here.
Regardless the hardware issues, the software doesn't sound very tempting if there are just 25 songs and no hope of downloading. more. I consider 70 songs to be too short for this type of game, so, 25 is simply anemic.
I think before you buy this, you should test it first.