@WhichInv thank you, it's working well for us - the problems I had with Vanilla were accumulated over time through my own faults and inexperience, other were ongoing issues with the software. I first installed Version 2.0 and instead of a stable version, opted for the latest development builds which I updated regularly. I was an early adopter of 2.1 and the dev builds of that version.
My main issues came with the database. A couple of times the normal upgrade method wouldn't quite cut it, so it was just as simple to install a fresh forum and hook up the database. Other times I used importer to fill the database. Over time, things went missing and sections of the database became corrupt and in trying to install the latest stable version, I'd somehow messed up the database trying to alter things and it was a lost cause.
The other main issue was a combination of spam and registrations. Vanilla is a magnet for spambots, and numerous measures need to be taken to ensure that they're kept at bay. Spammers 90% of the time were registering, flooding the activity feed (which they can access if you don't set permissions properly) and going, even before confirming registration.
There are detailed methods to prevent spam outlined in the forum at vanilla, but it eventually got so unwieldy that it put off registrations. For example, to register we had a "are you human" question (a sum), a recaptcha, username, password and "why do you want to join" question, on top of email validation, Stop forum spam, Akismet... so either new users were put off (unless they used SSO) or locked out of using the forum.
Then, for almost 5 months last year we were unaware people couldn't register because there was an issue with recaptcha; it didn't show on the registration page (that was a theming issue), I thought there wasn't one there and no-one could register because they couldn't see it to fill it in!
That's not to say I wouldn't recommend Vanilla - it is excellent, and has a wealth of plugins to get things done, with a busy support community - if you set it up properly.
I am enjoying NodeBB and though I promised I wouldn't use something in development again, I have been pleased with both its features and ease of use for our users - I wanted something similar enough to Vanilla for them to adopt.