I've been using XAMPP for years and really think it is the best and easiest LAMP/WAMP, etc. system to get up and running. I have installed multiple apps under XAMPP by downloading them from the developer's site, unpacking, and moving them into a sub-folder under htdocs.
XAMPP's move to using Bitnami caught me by surprise. I recently downloaded v1.8.3 of XAMPP for Windows and installed it as usual. Then I noticed the additional information on the XAMPP localhost startup page about downloading what I thought were additional apps from Bitmani. I followed the links and downloaded MediaWiki from Bitnami. I ran the install which ran flawlessly, and MediaWiki appeared at localhost. It looked like all was well.
Later when I went to the XAMPP control panel and tried to restart Apache, I found that Bitnami had installed a second copy of XAMPP with MediaWiki. The two copies were both contending for Port 80. Now I would have assumed that this special version of Bitnami/MediaWiki would have looked for an existing installation of XAMPP and install it there, but instead it ignored the existing version and proceeded to install it's own copy.
To me the power of XAMPP was the fact that multiple apps could be installed on one XAMPP server. Each app could then be accessed by specifying a localhost subdirectory (e.g., localhost/mediawiki, or localhost/subversion, or localhost/trac, etc.
I know there are workarounds. I can probably drag the MediaWikw folder from the Bitnami installation into my original XAMPP installation and fix up the links. But that's not the point. Logically it seems that Bitnami should add MediaWiki to the existing server rather than make a second copy. This would alleviate the conflict with port 80 which occurs when two copies of XAMPP are running.
These are just my observations as a long time user of XAMPP...