Actually I would prefer those on the keyboard, the only problem is that you loose some space there... But.... I think it is well worth it because navigating the code is something we always use a lot !

IMHO the right and left to move the cursor would need to be in the keyboard itself. Gestures are great but they are much slower than using a key, even in the capacitive keyboard. You could use just the 3 fingers for the other functions... 3 fingers, right word right, left word left, up page up, down page down. That would cover most of the essential navigation functions. 4 fingers would not be essential at all, they would be just a luxury :-) There is a app called writer that does a nice keyboard implementation where they have the cursor control on the keyboard, maybe it is worth to take a look at it, I can write pretty fast with it.

I am not sure how much control you have over the multitouch interface... If you have "absolute" control it would be nice to have something like: 2 fingers right, word right; 2 fingers left word left; 3 fingers right end on line, 3 fingers left, beginning of line, 3 fingers down, page down, 3 fingers up page up; 4 fingers down end of file, 4 fingers up beginning of file... I think those would not "conflict" with any of the existing gestures and would make editing and navigating trough code much faster. Novice user would not even notice that the gestures are there and "heavier" users can navigate better.

I completely agree, tabs takes way too much space. A button with recent files would have almost the same result and keep the screen looking less "clogged"..