TechnoPro, DHCP introduces new failure modes. Your DHCP server needs to work reliably, for example, which creates a lot of potential failure modes - what happens if your DHCP server is slow, and sometimes doesn't work but usually does? And there must not be another system on the network that is misconfigured to be a DHCP server (as deployed, DHCP has no security). And possibly this requires new local firewall configuration. And some OSs made near Seattle do sundry internal networking things a little differently with DHCP - new code paths.
All these failure modes add up to new ways for things not to work that won't be there with a static IP address, and thusly your network WILL be less reliable. So the question is: how much trouble do these problems cause, and how much other benefit (ease of administration) do you gain by doing it? Typically, once you get DHCP running it mostly stays that way for a while, so the trouble isn't much, but when you need to reconfigure your network and/or add new hosts, the ease of use pays off. So typically it's a good trade. But not always. For example, in a data center environment where we're talking about important servers, DHCP is unacceptable - even the small reliability hit is just too much.