For a long time, Dutch TV-makers had no budget for voice-over translation, which gave many children from the '70s and '80s an early advantage over their counterparts in countries like Germany and Italy. That's still noticeable, although more and more English cartoons have been translated over the past few years. It's still very rare to find TV-shows and movies that have been translated to Dutch, commercials are the only common exception.
Furthermore, we start learning English at the age of 10, which means nearly every Dutch person you will encounter will at least be able to understand you very well. Most of them will also be able to respond. The Dutch-English accent can be thick, but it leans more towards overarticulation, which makes it easy to get into. If you want to prepare yourself for that, Louis van Gaal's recently been appointed as the manager of Manchester United. His post-match interviews have it all.
One little piece of advice: when asking for the time or making dinner reservations, we don't mean half past five when we say "half five", we mean 4:30.
Update: @gerrit: Was it really about budget?
I don't have any sources for this (I tried to find some), so let me clarify what I do know. I've been told by someone who worked in public TV back then (note that we didn't have commercial TV until the late '80s) that it was a lot cheaper to add subtitles than translating the show and hiring voice actors, which was something the Dutch channels simply couldn't afford. I do suppose there's a big difference between voice-overs (like in Poland) and real "dubbing", but I remember that Germany also did voice-overs back then instead of dubbing, while they were on a significantly higher budget (including the budgets of other German speaking countries, like Austria and parts of Switzerland). I suspect that the low quality of Eastern-European voice-overs of the '80s and early '90s would simply not have passed any quality standard in The Netherlands, so @DavidMulder certainly has a point, of course. As for @Relaxed, I've been to Poland and their English is certainly worse than the Dutch's. Portugal and Greece speak the kind of English I expect from high-tourism countries: functional, but no more.
Also, I've read here that apparently, most Bulgarian voice-overs of American movies, for instance, were actually shot with hand cameras in movie theaters showing the German dubbed version of the movie after which a single person did a voice-over track. I suppose you don't need a big budget for that.
I did find a second source from a newspaper TV-critic suggesting that it was a budget issue saying:
Er was eens een Duitse filmcriticus met een origineel argument voor nasynchronisatie en tegen ondertitels: zo zag je tenminste de
voeten van de acteurs. Wijlen Richard Roud, filmhistoricus, had een
interessante theorie over de verdeling van Europa in nasynchronisatie-
en ondertitel-landen. Aan de ene kant bevinden zich Groot-Brittannië,
de Benelux, Scandinavië, Zwitserland, Oost-Europa en de helft van
Frankrijk; aan de andere kant Duitsland, Oostenrijk, Italië, Spanje en
de andere helft van Frankrijk. Die lijstjes deden Roud op de een of
andere manier aan de Tweede Wereldoorlog denken. Toen ik de Franse
ambassadeur in Nederland (je probeert eens wat conversatie) deze
Roud-theorie voorlegde, liep hij zo rood aan van woede als Louis de
Funès. Het had met iets anders te maken, met grote en kleine
taalgebieden. Want, bien sûr, nasynchroniseren is te duur in talen die
door minder dan twintig miljoen mensen gesproken worden.
Dat wij niet de voeten, maar wel de stem van Humphrey Bogart, Marlon Brando en George Clooney kennen, danken we dus aan een
eenvoudige economische wetmatigheid.
To summarize: He's saying a German movie critic once said that they were doing these voice-overs so that we would be able to see the actors' feet for a change. The French ambassador in the Netherlands contested that and said it was simply a matter of audience size, where countries with an audience size of under 20 million would simply not have the money to do it. I think the Dutch audience was way under 10 million in the '80s.
An interesting statement in this column is that The Netherlands started flirting with dubbing in the '90s which appears to have been lucrative enough to start doing it more, suggesting that we (and especially the younger generation) don't detest it as much as you'd think.