I dont understand why all these Lumia haters are commenting on a phone they know NOTHING about and probably havent even used it!
best mobile of Microsoft must read before you buy
Okay, I agree that the OS build it came with( i.e., Build 10586.29) is buggy and a little unstable but have any of these Lumia/Microsoft HATERS ever heard of the wordUPDATES?!?! - - - - - - TL;DR The LATEST build is 10586.107 which is just AMAZING on these brand new phones. Its worth it really.
There is an app available in the store called WINDOWS INSIDER( which is OFFICIAL) and once you configure your device using this simple app( the steps are really simple - even a child can do it), you can start receiving regular updates via the Fast OR slow OR release preview rings. For users who are not tech savvy - go for Release Preview( The most stable build). Then comes the Slow ring(gradual updates with bug fixes) and finally you get the fast ring(fastest updates but maybe a little buggy) .
IF you dont want to use the insider preview for whatever stupid reason, its totally okay but youll have to wait for a week from today to get .107 or even a higher build( in the end youll get the same build or maybe an increment to that build)
I have used a Lumia 535 which has a Snapdragon 200 Processor and this one - The Lumia 550 has a Snapdragon 210 processor. The 535 handles Windows 10 so well, so if you have little brains youll know how the 550 will perform(after updates).
So take a chill pill and definitely buy this phone if you are looking for a safe and secure experience with great stuff like Cortana, Office, cool MSN apps with the usability being smooth even after months of usage unlike Android which even after a lot of optimizations tends to slow down a bit.