Think carefully about whether you want a flat - more often than not newbuilds are money pits in terms of service charge and unless you're lucky the management company will be useless, money grabbing bastards.
However, having said that I appreciate a flat may be the only option financially.
Tips:
Like JT05 said, the lease is key. How long is left on it? Don't touch anything with less than 80 years to go and be prepared for the fact that anything with less than 100 years to go is going to cost you quite a bit to extend (assuming you might want to sell in next 20 years)
It's new, but how new? Has the NHBC 10 year warranty expired?
Go and ring on some buzzers and speak to the neighbours. what's the soundproofing like (unfortunately tends to be poor), how is the management company, how much is the service charge and ground rent, any issues with neigbours (I lived in a block where some people used to leave rubbish outside the bin store rather than in it, presumably because they had lost the key / were just bone idle...)
Parking can be non-existant or overcrowded if it is provided (people nicking your space - this is exacerbated by fact that Councils only give developers permission for new blocks if they agree that the residents of the newly built units will not be eligible for a residents parking permit. Many people don't realise this - whether or not it would apply depends on how old the flat you're looking at is...
There are lots of positives about living in new build flats - they look neat and tidy, they are warm and well insulated (thermally, if not for noise), low energy costs, modern appliances, fitted bathrooms and kitchens, but don't let your heart overrule your head when you see all the shiny kitchens and polished glass!
Good luck!