If this had been available when I was under 40 then I'd have put the maximum amount I could into it for the duration.
Further to what Travs mentioned, you can withdraw your money, tax-free, before the age of 60 to buy your first home. Otherwise you pay a charge of 25 percent (in effect losing all of your tax relief).
Whilst I have done well with my SIPP, which also has the same level of tax relief for basic rate payers, the lifetime ISA is tax free on withdrawal - as long as you are over 60 or using it to buy a first home, so a better option