I think those countries you’ve mentioned are great for a European SaaS startup. From my experience, the Benelux and Scandinavia B2B markets are ahead of the rest of Europe. I’m personally in the field of B2B marketing automation and I can safely make that claim for that specific market. I get comments from professionals in the DACH region all the time about how they’re jealous of where we’re at over here in the Netherlands.
Commenting from the perspective of being Dutch, I don’t think you’d need to worry about translating your app into Dutch – unless you’re targeting larger enterprises that employ an older demographic. The rest of the Netherlands (and also the Flanders part of Belgium) is savvy enough in English to give an all-English app a try. I’d imagine that Scandinavians are pretty English-savvy, too.
As for payment: in the Netherlands you should include iDeal as a payment option. It’s become a primary method of paying online. If you want to attract small businesses, it will certainly help attracting new customers. I imagine it’d be less of an issue with larger enterprises.
Hope that helps!
I first answered this question on Quora: