Even XenForo's default style better than UI.X. Being used by everyone doesnt make it better. It's just free, thats probably why most people using it but... It really suck.
1. UI.X isn't free.
2. Then feel free to use the default XF style.
3. It's wildly popular due to the fact it is very easy to customize, much easier than the default style.
4. Don't use it.
@bcercan I sort of agree with you.I am not fan of it in the least to be honest. It is overused and by now nothing original or special has been utilized with it. Twisted realms looks nice enough but the way UIX works would make me hesitant to join a forum that uses it.
Presently ready to purchase Xenforo+XMG to convert our Vbulletin forum but the one thing that bothers me is the lack of any quality themes for the software of Xenforo :/ I am going to try and reach out to one designer at pixelexit and see what they can do for us, but i am a bit disheartened at the quality of themes here, which is what makes me hesitant to pull the trigger.
I am actually a big fan of the default Vbullletin 4 theme and Vb5 themes. I actually spoke to soon. One of my favorite designers of Sultan themes actually makes Xenforo themes. We presently use themes from them. Our current theme is a heavily modified version of this one http://www.purevb.com/product/darkcore-vbulletin-skin/
I am also looking at IPB as a possible alternative to move from vbulletin. I am a bit unsure of their product but I do like themes from ipbfocus who does make themes for xenforo under xenfocus but i am not really particularly fond of the way they look on ipbfocus.
That being said I am not sure of the product quality of IPB. I know Xenforo is quite popular and I have a good experience using them as a visitor of other forums.