It will be choppy on playback, because you've put a slow filter into the video chain. This filter is for encoding, not real-time playback.
A sharpening filter will sharpen the noise as well as the real detail. Therefore you should generally put a denoiser in front of the sharpener. There are many available for avisynth, I use a plugin called dust (PixieDust) but it is very, very slow (takes me 14 hours to do one encode pass on an Athlon XP 2700).
(BTW I notice you are using VirtualDub to trim the video - it may be more convenient to put a Trim command into your Avisynth script.)