3.10 works pretty stable for me, the only bug left is peer widget duplicate ip keep growth 

Did you start from a fresh directory or with the previous .nxt files already downloaded.

just now, I'm getting this too

by the way, I'm running nxt under Ubuntu now, much reliable than Windows

are these .nxt.bak files normal?

Got this bug too in the browser.
After some restarts of the server part it went away.
The software apparently is still pretty raw and needs a few bugs squashed, but I like the concept.

I don't need any additional software to run it if I don't want to install it, just need a browser and can login to any internet server that runs the server part - is that correct?

Just purchased a few more NXTs at the exchange.

Why is block generation sometimes extremely slow (around 10 minutes)? I thought it should be one block per minute.

Not bug. Unimplemented functionality. Unconfirmed transactions not checked when they received as part of "getUnconfirmedTransactions" request. I'll fix the issue soon, maybe today.

BCNext wanted the "official" client to be called "Nxt Reference Software".

It's backup. If Nxt is not launched then overwrite *.nxt files with *.nxt.bak.