I moved from Android to Windows a few weeks ago. Amazing. And like you I'm glad to leave lag and bugs behind.
I'm a BIG fan of Windows Phone - I have a Lumia 1520 & have handed down my Lumia 920 to my wife
(she re-iterated yesterday,' ... she loves her phone, as much as she loves her car ... ' & probably more than me) jk .
That being said, there are enough posts on here about buggy devices (especially with Dev Preview), hopefully that will NOT be off putting, as ALL OSs have their share of bugs / glitches.
Don't want to turn a fan into a hater, if issues should arise. That's why we're here, the forum attempts to rectify issues, based on experience.
I have NO issues with my device, there were some early battery issues (after Dev Preview update 1 of WinPhone 8.1) that look to be shaking themselves out.
BTW: try
TimeMe tile, if you like a Time display on your Start screen - it appears to be very stable, NOW.