Been riding mine for 5 weeks now so happy to give a bit of feedback.
I’m 6’4″ on an XL, bought as frame only, running with:
140 mm Revs
Spank Oozy 345 wheels
GX 1×11 with 170mm cranks
XT brakes
Aggressor 2.5 / DHF 2.5 tyres
Firstly, the whole inquiry, demo and buying experience was a complete joy. Ben at Bird was extremely helpful and responsive with all my questions about geometry, particularly around the Reach and ETT numbers. I booked a demo and took it to Swinley (a place I personally don’t like riding on a hardtail) and was totally sold.
I’ve been riding it on my home trails (Wilts / SW) for around 5 weeks and am so impressed with it I haven’t touched my full suss during that time. It climbs well, it descends brilliantly (Strava says its as quick as my FS). It’s stable and confidence inspiring yet fun to muck about on, it’s pretty light and the volume of the 2.5 tyres give great comfort and traction. I was concerned about the BB height but haven’t had any pedal strikes. I love it!
I think this review sums up my thoughts on it perfectly.
http://www.bikeradar.com/reviews/bikes/mountain-bikes/bird-zero-29-first-ride-review/
If anyone has any specific questions am happy to give a view.