Well, all except for one niggle..........WP8 KEYBOARD Y U NO CAPITALISE MY 'I' EVER EVER?! I'm fed up with typing an i and having it not capitalised. In fact, in that last sentence (and this one too) i had to go back and force the i to be lowercase because IE10 in W8 autocapitalises it. MICROSOFT, NO! I AM A PERSON WHO ACTUALLY WANTS TO USE CORRECT GRAMMAR ON OCCASION. DON'T PUNISH ME
I'd suspect that perhaps you may have (by accident) tapped the add button with a lower case i, and now it has that i in its dictionary. Mine capitalizes the I no problems. Try going into Settings | Keyboard, tap the advanced button, and the reset suggestions button, and see if that fixes your problem.