i'm sorry, i don't get this - LR3 has lens correction, but only from CS5 ??!!
I think you're confused here. Lens correction IS available in LR3.
As I understand it, the reference to CS5 is with respect to the lens correction module in LR not being able to access the pool of extra user uploaded lens calibration profiles. The lack of this facility might just be an oversight that's rectified in future bugs fixes.
It's another question if that is something you need anyway. User supplied profiles might
be very good or, if poorly made, worse than the defaults.
I assume that it's possible to build your own with the lens profiler download from Adobe labs and install them into LR3.