hello mrgas
the ND filter you've linked to is a 2 stop filter ,yes i'ts a starting point but no more than that .
in some situation 2 stops might not be enough or too much ,the usual set up most folks have myself included is a set of 3 namely 1,2&3 stop filters it covers a lot of situations even moreso when you use 2 of them together. ..
the other thing to consider , what if you buy another lens with a filter thread larger than 52mm ??. do you then buy a second ,larger filter to suit ..
you can get slot in filters including NDs amongst others ,you then buy 1 holder & adaptor rings to suit the lens each adaptor ring costing approx £5..
cokin is 1 make that use this system if you have a look here
http://www.cokin.co.uk/pages/main.htm
it will give you a rough idea of what i'm jabbering on about & will probably make more sense.
and here might also help you understand a bit better.
http://www.cambridgeincolour.com/tutorials/camera-lens-filters.htm