To answer your question, I am staying with KitKat 4.4.4, there are far too many bugs to apps that I use, and more importantly wi-fi issues that people are experiencing since upgrading, so it's a big fat NO to Lollipop from me.
The only issue for those like me that are staying with KitKat is that they won't be able to use the What's New app for updates to their Sony apps, I say this as this will hold all the updates for Sony apps on Lollipop and beyond.
It will be interesting if the update centre will show new updates for apps now that Lollipop has surfaced, I would like to think that the current Update Centre on Sony smartphones will continue to work until you upgrade, it should, especially if you decide to go for Lollipop, but I am thinking more about app updates on it.