I use POE::Wheel::FollowTail to parse, analyse and forward events concurrently from two very busy logfiles (each about 100M a day, average 10 significant lines per second, picked out of three or four times that many, peaks way above that). I have POE look at the file every five seconds and the CPU hit is negligable compared to other processes on the box. I guess it queues itself an alarm between checking the file as this particular POE is doing little else (throws an I'm alive event every minute just in case).
I like the fact the FollowTail handle the log file being rolled over, tells me about errors without choking and generaly just does the right thing. It saved a lot of thinking about all the corner cases (in my case these files are r/o NFS mounts from elswhere and occasionly mis-behave) and let me concentrate on the interesting bit.
Pereant, qui ante nos nostra dixerunt!