It is possible to connect the LEDs up without any kind of level shifting, however mileage varies from strip to strip. I have one setup like this, and one with the full logic shifter. This can work because the spec of the LED strips means they need 0.7 * VDD(5v) which is ~3.5v. Close to the Pi's 3.3, so depending on how tight of a tolerance your strip has, this is possible.