No problems at all with Debian so far.

I started with CentOS but found it difficult to maintain and set up. Then I switched to Debian because for some reason I felt pressure to not use Ubuntu. People often imply that Ubuntu is for bad programmers, inexperienced people, etc. It's kind of like "well, all the cool kids are using distro X because we're l33t and you're not cool because you use Ubuntu" so I stayed away from it for a while. Finally I ended up deciding that it was more important to just get a fucking app running on a server I could most effectively use. I'd been using Xubuntu and Crunchbang on my laptop for a while and so I made the switch and I'm very happy with it. I subsequently redeployed all my VPSes with Ubuntu 11.10 or 10.10 depending on what the hosts offered. I like it because not only is it the easiest for me to manage but it seems like its easier to find help for any problems you may run into and good documentation.

I say screw the hipster crowd who are too cool for Ubuntu and just focus on what's best for you. I think people like that are trying to convince themselves of how great they are more than anything else.

Be a l337 hipster with your desktop if you must, but for servers go with what has had the most man hours put into its evolution toward stability, performance, support (aka, it just works). In that regard, if Ubuntu is good enough for Facebook's servers (I hear, but haven't verified) it's good enough for mine.

Mot vendors offer a PPA for easy integration with apt on debian. MongoDB, Maria/MySQL/Percona etc. This way your core system stays solid and well tested, but you can build your app layer using whatever version you want. It's definitely a win-win.