How accurate is accurate????
the GW60 is very convenient, there's a thread about it on this forum.
It has "SDoP" output which gives an indication of accuracy for each point, typically 0.2kts.

So here's the 2s results from my GW60, you can see the +/- values are between 0.111kts and 0.232kts
It's also 5hz which gives good definition at short times.
It's somewhere between $360 and $300, I think Surf Sail Australia have them 20% off at the moment.

And here's the tracks from it loaded into GPSvisualizer.com colour coded by speed