the source footage is never greater than 60Hz so its of no use going for 120 hz or more. if you think higher refresher rate can provide you with more details then you are wrong.
Actually, higher refreh rate tvs can produce a distinctly artificial, unnatural feel to video. Motion can appear too smooth,action can seem just slightly sped up to the point of looking unreal, and it can take you out of the experience quicker than any judder. Indeed, for me, judder is just as natural as film grain, and a subtle but necessary part of watching TV and movies.
If you get blur its due to interlace on Sd channels.
Interlacing is not used on hdtvs nowdays and progressive scan is used.
Progressive is just like an xerox machine, copies the data and reproduces at the destination whereas interlace reads only the alternate lines(from left to right) and reproduces at
destination.