The package costs £21 per month: £11 per month for the line rental (the same as you'd pay to BT), plus £10 per month for the Talk3 element. There is also a one-off fee of £30.
The Talk3 International Tariff includes calls to the USA (including mobiles) for 2p/min anytime. The domestic tariff has free UK landline calls for the first 70 minutes, and 2.7p/min daytime (0.9p/min evening) thereafter.
So is it worth it? I'd say that it depends on what the quality of service will be for the broadband. There's nothing worse than having a problem and having customer services being clueless or unavailable. Also, broadband providers can vary wildly in the quality of their Internet connections, and this can greatly influence reliablity and speed of your connection.