The average high frequency rate of televisions of a similar age and spec to this TV is 220Hz, and the high frequency rates range from 50Hz to 1,600Hz. At 400 hertz, the 42LA660 has a quite fast high frequency rate compared to most of the other medium display diagonal TVs that came out around the same time as this TV.
Alternative 400Hz refresh rate TVs currently available which you might want to look at include the UE40ES6800S, or the UE40F6510SB both from Samsung or the LG 47LA691 which all of have better reviews.
If this LG TV high frequency rate is not fast enough for you then you might want to consider the UA40H6400 (480Hz and higher rated), or the UN46F6400 (480Hz and higher rated) both from Samsung or the Panasonic TX-L42ET60E (600Hz and higher rated).
What does "high frequency rate" mean?