Traveling by train is one of the most convenient means in Benelux. It will take you 3 hours at most to get from the Brussels airport via Antwerp right to the center of Amsterdam by rail if you take a regular international connection ( http://www.b-rail.be ) and you can travel by rail event faster if you take a a Thalys train ( http://www.thalys.com ).
In Belgium, unlike Holland, train connections are more regular. Surprisingly maybe but it’s a practical fact that in rush hours Dutch rails are often subject to traffic jams or computer systems halts… Therefore, when you take a train in Holland be prepared to be asked to take a bus instead (provided by the rails operator) to continue your journey.
Traveling by train can be a lot of fun for younger groups that travel across Europe but also for those who prefer to relax and drink more than one glass of beer when they are on a road. (Local laws in Belgium, Netherlands and Luxembourg allow 0.5 milligrams of alcohol per milliliter of blood.)
Last but not least, rail connections to the airports in Brussels and Amsterdam are so amazingly convenient!
Enjoy your journey! 😉