[Xperia Z2 Tablet Q&A, Help & Troubleshooting] FluidDruid:
Yes. I used this guide - http://xdaforums.com/showthread.php?t=2792056 and it worked flawlessly. Rooted in just over a minute.

I've not seen any audio lag. The touchscreen isn't the most responsive I've ever used, but is fine with fingers. Stylii are a different issue - I've not found one that works well. I've not seen any lag whilst using the tablet (except for the odd microstutter when Google play decides to update everything at once). I updated to the latest firmware as soon as I got it, so I don't know what these were like before.

17.1.1.A.0.402 is the latest, released at the end of May.

All KitKat devices restrict apps writing to the SD (Astro for example would only be able to read the SD). By default you can only write to the SD by plugging into a computer and copying files across. However, if you're rooted, you can just install SD Fix (https://play.google.com/store/apps/details?id=nextapp.sdfix) and get the pre-KitKat behaviour.

They're a little low, but the tablet is so light that you're not likely to be gripping it hard enough to distort the sound. Personally I tend to hold it one handed in landscape like I would a book, with my thumb on the front of bottom edge and my fingers splayed out on the back. This way the speakers are completely unobstructed.

I've not charged from empty, but using the charger it comes with seems pretty quick. I can put it on charge, go make a cup of coffee, get back and it will have gone up by a percent or two. I bought the magnetic dock, and just leave it there when I'm not using it. The battery easily gets me through a day of heavy use, and when I'm at home it just sits on the dock.

I had exactly the same thoughts (also in the UK). 32GB is the way to go. I've had mine about a month now. I've installed pretty much every app/game I'm going to need, and the internal memory is about 80% full.

Some more thoughts:

Pros

This thing is so thin and light that I forget I'm carrying it in my bag. For me, that's a huge bonus over other tablets, and more than makes up for its flaws. It's noticeably easier to hold than an iPad Air over long periods.

Sony's interface is very close to stock Android, and most bloatware (of which there is very little) can be uninstalled.

Waterproofing is nice to have. I thought it was a gimmick at first (does anyone actually use these in the bath?), but I use mine to display recipes whilst cooking, and it's nice to not have to worry about splashes and spills.

Vibration - it lets me know that I've turned it on. I wouldn't miss this if it were missing, but it's nice to have.

NFC. I love NFC. I have a tag on the bottom of my universal remote; I use the remote to turn on my Hi-Fi, swipe the tag across the tablet, and the tablet connects over Apt-X Bluetooth and starts Spotify. Magic!

Dual-shock compatibility. It just works (you need an OTG cable for the initial pairing, after that it's Bluetooth), and is very slick.

Cons

Screen resolution isn't as nice as other tablets. This isn't noticeable when used normally, though if it's closer to your face (e.g. you're lying down using it in bed), you can see the pixels.

The waterproof flaps on the SD and USB connectors feel a bit flimsy. I'd highly recommend the magnetic doc, or a connector adapter such as the Magnector-X for charging, so that you don't have to open the port covers.

It's a fingerprint magnet (but you can just wash it clean, because it's waterproof).

The IR blaster seems to have a very narrow "beam" so is a bit tricky to use. There is also a ~1 second delay between pressing the onscreen button and the IR signal being sent. I've given up on using it, but I'm not sure how much use I'd have gotten from it anyway.

I'd go to a store and have a play if I were you. Try and find one that's not got a huge security lock on it; I've seen this on display in some stores with a metal cage around it, or a huge self retracting security cable, which makes it hard to get a feel for how it would be to hold.