Amsterdam is somewhat of a creative hub here in the Netherlands, with a lot of designers, photographers, advertising people and other creative types. There are also a number of good, but relatively expensive, data centers where you can host your servers. It has never really been a technical hub, though. Most technically focussed businesses (including startups) in the Netherlands seem to be in places like Eindhoven (with the technical university and Philips campus at its core) and other towns with technical universities, like Delft and Twente. Amsterdam is a bit of a hipster town, like people who work in advertising or make iOS applications, not a nirvana for nerds. One of the exceptions seems to be the CWI at the Amsterdam Science Center, which is were Guido van Rossum started working on Python.
That being said, there is some technical talent in the Netherlands and distances are small enough that you can attract people from towns like Eindhoven to work at a startup in Amsterdam. Most people also speak English, allowing easier cooperation with foreign co-workers and customers.
Downsides of the Netherlands are bad conditions for immigrants, high taxes (expect to pay over 50% on income tax alone), high cost of labour due to all kinds of government enforced perks like daycare and a lot of free time, business-unfriendly labour law, bureaucracy and the lack of an entrepreneurial culture. Technical and scientific education is also declining in both popularity and quality, despite the half hearted efforts of our government to position the country as a "knowledge economy". Getting a visum is relatively easy for immigrants from the EU and US (there is a special treaty with the US to enable easier immigration), but immigrants may be forced by the government to participate in expensive language and integration courses due to a streak of xenophobic politics in the last ~10 years.
Amsterdam has a reputation as a liberal city and a "gay capital". There seems to be some correlation between a vibrant gay culture and tech hubs, if you look at Tel Aviv and San Francisco. I hope that Amsterdam can turn the current decline around in that respect, because the city isn't as gay-friendly as it used to be anymore (according to the homosexual community; I can't report from first hand experience here). Homosexual couples are apparently harassed and beaten by groups of second and third generation immigrants from muslim countries (whom are quite prevalent here). A homosexual couple (or visually distinguishable Jew for that matter) will get harassed, bullied out of immigrant neighborhoods and in some cases physically threatened or worse. This development is accompanied with a rather ugly, xenophobic and isolationist political movement rooted in the lower middle classes that feel left behind in the current economy. Their main political hero, Geert Wilders, gained popularity by constantly picking on muslim immigrants in the rudest possible manner and is currently heading the second biggest party in Dutch parliament. The other parties have silently adopted a similar tough stance on non-Western immigrants to retain or win back voters, but usually without the ugly rhetoric. The tolerant atmosphere that brought intellectuals from Descartes, to John Adams to Einstein to our country seems to be in peril.
I think Amsterdam has potential for startups. Particularly in the creative and mobile apps industry. That being said, the current entrepreneurial atmosphere in the Netherlands isn't great and I doubt that we will be able to compete with places like Silicon Valley. I think it won't attract many foreign founders before some of the cultural problems are solved (I'm pessimistic and distrust any government initiatives in that respect because politicians won't be able to create a startup culture) and the town becomes a local tech hub in its own right (competing with towns like Eindhoven). But this is a cool initiative. I'm sure it will do at least some good and will be valuable to the participants. I'm not in Amsterdam, but as a Dutch hacker I might drop by one of the meetings at some point.