Okay... there's a question I've had for a while. If you're a native speaker, you can help!! If not, perhaps just hear my case; maybe you'll delve a little deeper into pronunciation.
Listening to this sentence, you can hear two different R's. One of them is a guttural-type trill as French has (hert, on slow audio), while those in korte and staart both sound much like our English R. Yet, there's more.
If you listen to those Dutch pronunciations of "Nederlands", you may notice that three of them (one from Holland, two from Belgium) sound like that alveolar trill you'd hear in Spanish (NedeRRlands). And this happens all over the place—there are three different R's in Dutch, not to mention an H and a G that (when said too quickly) can also be mistaken for a guttural R.
http://www.forvo.com/search/hert/nl/ - [heɚt] and [fliχɔnt hert], in IPA...
Here's my question: Does the significance of the trill (or which trill) matter for distinction between one Dutch word and another, or sometimes here but not there...? Or does it simply vary by region/dialect?
There is absolutely no meaningful difference between the various possible R sounds of Dutch. It's just regional variation.
For the most part, it's pronounced as a trill (like Spanish or Scottish), which can become a tap between vowels (again, like Scottish), and some speakers pronounce it like the English R at the end of syllables.