Well, there is no "catch" as such - Telstra are pretty open about the whole thing. The value of the free laptop is $700, which does restrict choice, but if you want a better specced model you can pay the difference. It's also a 36 month contract, with a minimum cost of $3,564 plus excess usage charges. I guess with just 1GB included, the whole excess data cost of 30c/MB could be considered a bit steep, but it is Telstra, and their mobile data charges are fairly well known for being expensive.
The arrangement is done exclusively through selected dealers including Harvey Norman, ICT Distribution and Techhead Interactive, and the deal ends on June 30.
It's a really good idea, and hopefully we'll see some other networks follow the big T's lead on this one. We've all been signing up for subsidised phones on 24 month contracts for years, so hopefully it will work for laptops as well.