This is concerning - I noticed a certain slugginess of web pages with tables as well. I'll soon do some profiling and load tests as well - what you noticed is a concern, especially that after so many calls HotSpot would have compiled that code to native instructions. Thousands of calls to those methods to render a page - ouch.
I see nothing much happened on the page about Seam's performance for over a year. Ouch, ouch :-(