HTML5 is really famous these days. I want you to add HTML5 feature in Slimboat if you wish it to be an advanced browser.
And I think flash is a must. My flash download never completes in Slimboat. It stops somewhere at 99-100%. Add built-in flash player for this problem to be solved.
Adding both would be a good idea.
Using: Slimboat 1.1.24(Latest as of 4th March 2013)