I made so many mistakes on the virtual keyboard that I decided to try the BT wireless keyboard. It's much better for entering copious amounts of text or posting comments on this forum.*
It's nice to have a TAB key, arrow keys, and function keys (volume, brightness, play/pause, etc.). I find SHIFT+arrow an easier way to select a word, Command+A a better way to select all, and Command+X, C, and V a faster way to cut/copy/paste. Characters like %, _, and + require two key clicks before they appear on the virtual keyboard. They always are there on the BT keyboard.*
So I carry the BT keyboard wherever I go in my messenger bag along with the iPad. It only weighs 11 ounces. (The keyboard dock weights 24 ounces -- as heavy as the iPad -- too heavy to tote and too thick to even put in my bag.)