What do you mean by leaky? I have just built a sallen-key circuit of this and I see some (relatively) high frequency noise on the output, even though the input looks clean. Is that what you mean?
Sort of.
More precisely:
The high frequency attenuation is limited by the output impedance and GBW of the op-amp. Typical stop-band attenuation is in the -40dB range, i.e., it's rather "leaky".
If all you're ever concerned about is the domain of "what you see on the scope", then nevermind -- you can't resolve more than 40dB of dynamic range on a scope display.
If you're concerned with small signal behavior, high dynamic range, sensitivity, precision and so on, this will be a problem.
The op-amp also adds noise, which: if you don't see it on the input and you do see it on the output, then that's noise. It shouldn't be much (microvolts), unless your circuit or amp are bad (poor design or poor quality).
Tim