Here's my attempt at the 300 style special effect. It works quite well for the HV20 with its high resolution picture and choice of manual settings. Good light is important to allow TV-500 or TV-250 mode. This eliminates motion blur. Shoot from a stable platform to reduce obvious rolling shutter. Then capture your 60i.
Convert your 60i to 60p using your choice of deinterlacer. Smart Deinterlace based on VirtualDub's works quite well. As for the codec, choose one that supports 60p such as Lagarith/Uncompressed AVI, WMV or H.264. Then feed the clip to an NLE that can do velocity envelope/time remapping. Speed up/ramp up the broad movements while at wide. When you find the terminus of an action, back off a bit then slow down to at least half normal speed (I like to go down to 0% in a V or U for Vegas velocity envelopes). Keep that for a few seconds then return to normal. To accentuate the slow mo portion, use digital zoom to the area of action.
Sony Vegas example: