Well i had Sony Xperia P for over 2 years and I loved Sony phones. Loved means i was in love coz it's a SONY and got over with it for performance, camera, software, app bugs on xperia p. I've heard lots of bugs, issues with sony from my friends. I treated like a child but gave me herpes.
Now using a LG G3 (D855 3GB Version). Best phone ever. Awesome battery performance. Stunning superfast camera. Going to shoot a video with 2k resolution for an assignment. I believe we will have awesome video quality. Display? Super clear. got built in AI system from LG to remind about frequent calls, text messages, junk memory, memory improvement tips, phone temperature control etc.
Running over so many live update apps with 4G and Wifi on. 2 days + battery performance on Auto brightness mode.
(gmail, microsoft exchange server, viber, skype, whatsapp, facebook, facebook messenger, swarm, instagram, security suite, anti theft app, google location report, rebtel calling app, linkedin etc). Still using stock theme came with the phone. Awesome interfaces.
I love the sony xperia z series camera but still i've heard few bugs the phone.
another reason for disappointment with sony is they release a new phone at least a month and no matter the latest phone you buy, it will be the historic phone on sony after 3,4 months.

But i still have hope for a sony coz they have the best waterproof, shock proof devices with a awesome camera with tweaks. But Xperia P, T1 are like the 1st, 2nd generations of the sony phones. of course we should expected it need few improvements. My gf is using Z1 and even though still new had few bugs on the phone. Stock OS, few apps running for call me. But fingers crossed for sony's latest phones such as Z2, Z3. I've heard Z2 is best from sony family. So i guess starting from z2 they are on the right track.