Totally true JesterOC, but the declaration has to be reasonable. You could create a 3 shift aspect called 'strong as a bull' and use it to help pick up a car, you could in theory create an aspect called 'godlike strength' and use it to launch that car in to the sun but it's going to cost a lot more shifts.
With gravity you are lifting yourself, lighter than a car and perfectly reasonable. You choose the flavour for it so you can reverse gravity and be launched skywards, you can negate gravity and gently push yourself away from the floor or you can call it low-G and just bounce to where you need to go. However there is a huge difference in shifts between using magic to jump over a 6' fence, jumping on to a rooftop, leaping over a skyscraper or launching yourself in to orbit.
Now obviously jumping on to the rooftop of a small building is on the smaller scale of things but even so, it's not a one shift spell. Basing the power of the spell on the border level seems like an appropriate thing to do, but perhaps a different difficulty scale is required. I was using the concept of +2 is an analogy for the strength of a 3 shift manoeuvre, I assume putting more power in would provide a larger bonus though it's not in the rules as such. A different model, as Tsunami suggests, is needed.