I moved into a new build, a 1 bed maisonette. As a tradesman who has worked on plenty of new build sites, I know they aren't necessarily always built the best (get a showhome/ ex showhome if possible) as they are usually best built. But of course you get good ones with hardly any issues (luckily I did) or you can get nightmare builds with snag lists as long as your arms. So look into the home builders first. And if possible when viewing if you have any friends in the trades to come along and look with you is handy!
Besides from the builds themselves I found it could be difficult for your average Joe diyer to make many changes to personalise and make more homely with things like hollow and non load bearing walls, very little room to change out things like units, bathroom, furnishings unless you go like for like. With the walls also being thing and not the best, you often get alot of noise traveling between flats etc.
Money wise where I lived seemed good value for money when compared to older similar properties. However there was lots of fees, which in my case added up to around £3000 a year with ground rent, 3 maintenance companies (which were hard to get to do anything) and a company which we paid to look after the greens, parks and ponds and never saw for 2 years. Which worked an extra £250-£300 a month ontop of the mortgage and bills.
The last downside I would say was the parking and street/road layout, with thin roads and pavements which usually had cars park half on the paths, grass or blocking drives, luckily I had 1 allocated space in the car park behind, unluckily if you have an average sized car or above you'd be lucky to comfortably park and access your car if your neighbours were also parked up.
But on the plus side it seemed to be a nice community with varying classes of people, ages and races. Not much worry about repairs to your flat etc as all is new. Was always a nice area to walk, take the dog out to the fields, usually plenty of parks and communal areas etc.
I wouldn't be against a new build in the future however I would avoid a new build flat or maisonette and would go for a house instead.
Sorry for such a long post, was just trying to cover all aspects