James Robertson has published a concise review of the pros and cons of dynamic vs. batch publishing in web content management systems. He also covers the hybrid of the two, which is what we now have in place with our systems at work.
The major con under the dynamic system that I have experienced directly is the server load issue. Dynamic systems cannot scale up for additional traffic as efficiently as batch or hybrid systems. Authoring activities are very processor and database intensive operations. Mix a few active editors along with heavy end user traffic and your server may quickly succumb.
About 18 months ago, we were in the unenviable situation of limiting editing activities to a small number of staff during low-traffic time periods. Without those restrictions our site constantly crashed and/or timed-out due to the unmanageable load of end users and editors hitting a single server. Not a popular measure with staff, to say the least. The dynamic CMS we were using at the time eventually came out with an update that allowed us to move to the hybrid approach and lift our editing restrictions. Moving authoring to a separate server dramatically improved the stability of our production web site.