Question: I am looking for a visual tail tool that can monitor several local or remote log files.

Optional features that interest me: color highlight based on log error level, coloring for special words, filtering of messages and/or notifications on new activity.

Answer: 
You may try to use a combination of `multitail` and `ssh`.

* <https://serverfault.com/questions/53976/use-local-tools-to-monitor-remote-logs>
* <https://superuser.com/questions/320575/mac-os-x-logfile-viewer>
I found a tool that can do this [GeekTool](http://projects.tynsoe.org/en/geektool/), it even has a version that works on Lion (see the forum).

It can be used to do just simple tails, without filtering or other stuff, so maybe someone has a better alternative.