i have set up and installed many different cms's to test and run. Here is what I found out hope it helps.
xoops - very easy to set up and install. Easy to work with templates. Management of users is not the easiest. Also, not all mod's work with the newest versions and difficult to find some good ones.
<- one of my sites been running with no problems for about 6 months
phpbb2 - great for forums. I ran into a few security problems but if you keep it updated you shouldn't run into to many problems. If you are setting up a WoW guild phpbb2 has many great mods.
phpbb2+ - phpbb2 with a portal interface. Pretty nice improvement of phpbb2. My phpbb2+ site was running for about a year with only a few slight security problems.
joomla - my personal favorite. Not as easy to intergrate forums into it as others but not that hard. TONS of great templates and mods available. management is extreamly easy.
<- one of my sites...not finished yet
phpnuke - probably my least favorite. Management sucks and hard to find good mods. However, it is very easy to make it look professional.
SMF forums - I have run in little to no problems so far. Great system. I currently working on intergrating it into joomla. Not the easiest to intergrate but you can always just wrap it or configure the templates to look like your site.
example - www.axiompvp.com
go to forum
I have played with a few other cms's but there are the major ones that come to mind. Personal recomendation is as follows:
joomla - probably the best all around.
phpbb2+ - many great mods for guilds such as WoW.