I just wanted to add the first part of this makes no sense because IPB Is not open sourced software like mybb, phpbb, smf :yum:
IPB4 did have a lot of bugs. But then again this is a rework and a completely new product, that's annoyingly expected for new software. No software is bug free and will have issues. What IPS had issues with is the fact that they rushed updates out without testing as strongly as they should and it ran into issues later when they released updates that caused issues and had to turn around and release fixes.
IPB4 is perfectly usable for forums. I can link a few million post forums as well as my own 550k forum (When we switch back).
We've done Xenforo and IPB and despite IPB's glitches and bugs(which are quickly worked on, improved and fixed), I'd take it over xenforo any day :yum: