I used the LCY service last weekend for a last minute Olympic trip. Got two seats on my Avios (BA Exec. Club) for £27 total, booked only 4 days before. Great flight and service, with hot breakfast, (forgot such things existed after using BE to LGW for so long), 80%+ load and arrived at LCY 20 minutes early.
All that said, the cash fares are not really geared to the leisure traveller, so won't be doing it too often. Back to FlyBe and Southern Railway!