Hi,
I owned one plus one and one plus 3t. My current daily driver is one plus 3t.
One plus is offering a flagship phone for half the price of some most expensive companies. One plus devices are future ready. My 3t runs very smooth and never faced lag. AAA games are buttery smooth.
Website is well designed, easily navigable.
Pros of purchasing One plus device:
1) Affordable flagship devices.
2) Variteis of back pannels for your device are available for purchase on their website.
3) Goodies like bagpacks, tshirt and much more available for purchase on their webstire.
4) With the purchase of new device from one plus, you get a voucher worth 300 inr. You can use it to purchase accessories for your device. ( from official one plus website)
Cons :
1) Aftermarket service are very bad in India.
2) Bad customer service.
3) Accessories of device will be discontinued within a year of release.
4) Devices are cheap, but when you damage your device and give it to service center they will cost more money than then original phone.
For exp: if you broke your screen and went for replacement, it will be very expensive.
Overall the devices produced by one plus are great, affordable, future proof but the aftermarket service of one plus is in India is worst.
I had one plus one and used it for more than 3 years without any problem. And still it is working fine. For upgrade I purchased one plus 3t and I am using it since 7 months and I faced no problem till now.
Hope one plus improve their after markeservice. I rated one plus very good only because of the quality device they offered at very affordable rate.