I have used many many SIPs...just about all the freeones that are available.
FingerKeyboard 2.1 is...simply amazing
http://forum.xda-developers.com/showthread.php?t=501122
every other SIP i've used...since my fingers are so fat...I seem to miss the right key and end up having to backspace a bunch. But for some reason, with this keyboard...it's like it knows what word I'm trying to spell and picks the right letter...it's accuracy is amazing.
I just recently started using it with two hands....in PORTRAIT...and I can WALE...
I normally don't pump up a piece of software like this...but I really believe in this one.