I've never had a bad experience with these guys...the food is hot when it arrives and I've never had them mess up an order. Even the delivery fee isn't outlandish.
However, it's not a perfect service because the prices on the Waiters En Route menus are a fair bit higher than the restaurant's own menus...which means it can be an expensive option.
That said, I'm willing to pay extra for convenience - and they're definitely convenient! We love ordering from Ruan Thai.