Actually, I notice typing with an external USB keyboard sometimes lags, too. This morning I was typing in a post, and looked up to see only half the sentence completed and ticking along at about 1 character per second. It's not just landscape mode, and I can't pin a pattern to it. Sometimes the keyed input lags terribly, most of the time the input is in sync as fast as I can type. Maybe there's some kind of intermittent/background process that occasionally interferes.