Normally in the early phase of the game you will need all different colours so no cards you pick up will be wasted. I will only pick up a face-up locomtive if I need it to claim a route that someone else appears to be going for or in the end game where I need one more card for a crucial route. This is because Ticket to Ride is a race, and by taking one card rather than two you are falling behind in the race. I agree with that. Early game I'll usually take trains from the top of the deck unless there are cards face up that I need right away for a crucial route that looks like it will be contested. As he said, you usually need all colors eventually, so getting random cards is no big deal in the first third to half of the game. Mid to late game you have to switch to take fewer random cards, otherwise you can miss some key routes or end up with way too many garbage cards, but early game it's a key way to get locomotives without falling behind in card count.
Other than that I think I agree with most of it. I've won a few games by ditching my long ticket and racking up close to 10 total tickets, but it all depends on how well the tickets fit together.