nc,
I don't have the transmission lag on my 05......but ours here in Canada are 'tweaked' slightly different than the U.S. models for emission purposes so I can't comment. From what I have read about the issue however not all owners of the ES complain about this.....only some.
Only other issue is the steering knuckle that is very common.....have the dealership replace it, if not already done so. Get the service history & I suggest the 2005 model over the 04 because of the slight upgrades they made (new tail lights, facia & some interior items). The 3.3L V6 has a timing belt & needs to be changed at 90k miles.
Here is a link to some of the items that were updated on the 2005 model mid cycle 'refresh'...
http://www.canadiandriver.com/buyers-guide...lexus/es330.php
And a test drive link (keep in mind the price is in Canadian dollars)...
http://www.canadiandriver.com/articles/bm/05es330.htm
And one more...
http://www.nctd.com/review-intro.cfm?Vehic...p;ReviewID=2765
Hope this helps & good luck!