Introversion have made some great stuff, I've owned for years and played plenty of Uplink and Defcon (bought Darwinia but didn't really take to it). Only one reason I've not bought this, and I thought I'd drag it into the public realm!
£17.99 is a bit pricey for what it is. 30'000 people might disagree with me, but there might just be another 30'000 people that have already voted with their wallets, not to open them!
If it was £9.99, I probably would be playing the alpha right now instead of posting this. Of course I can afford £18, but the point is, it's not worth that much to me. And it's a shame

Just saying! I know lots of people are probably gonna disagree with me, and yes, developers deserve remuneration for all their hard work, but at the end of the day, 60'000 x £10 > 30'000 x £18, and it gives a lot more people a chance to enjoy it.