I'm really happy with my Flightline 1 27.5. The geometry is great and at this price point, you're not likely to find a better set of components (with the exception of the front strut). The geometry gives it snappy response on the trails and the Shimano shifters (when kept in tune) can keep up with dynamic terrain. It is also capable of some trick riding, including wheelies and stoppies, and the bike is relatively light.
However, the front fork assembly leaves a lot to be desired. Within a month of medium level riding (mostly city and roads, some trails and tricks) the front strut was nearly shot, jumping and stuttering on both compression and release. Quite a bit of the internal grease leaked out around the seals, and the preload knob started to seize up. I would definitely expect to have to replace it within a year of riding.
Also, a sideways force (such as standing on one pedal) will cause the front wheel to flex out of plane at least 3/8 inch either side, resulting in brake rubbing (the rear wheel does flex some too, but not as much). It's not a safety hazard, but it can take you by surprise on a trail when the brake engages in a tight turn. The bike does have mounts for disk brakes, which would likely eliminate that.