The servers are already live, and people are already playing, but if you're yet to pre-order, or fancy getting a better deal for the game on PS4, you can grab Destiny for just £35 over at Tesco.
You'll need to create a new Tesco account and then use the eCoupon code TDX-HQ9T to get the game at this price. Also worth noting that you'll get exclusive content with the PS4 version that you'll have to wait a year for on other platforms. It will not, however, include the Vanguard Armoury DLC as that's exclusive to GAME here in the UK.
A tip of the cap to Barrons at HotUkDeals.