It depends where you are and how much you want to use. Where I am in Bonn, 02 offers HSPA which means fonic and Alice are a great deal depending if ou want to go daily or monthly. Alice offers a month-by-month flat for 20 Euros.

If you can bear going HTTP only via a proxy, Vodafone offers their flat for 10 Euros per month. I've been using this for 2 years now and never hit a limit.

On Vodafone and T-mobile, expect to pay 30-35 Euro for the 5GB open, high-quality internet connection.

I am likely to take a Vodfafone voice+data contract next year again but at the moment I can't find a data-centric plan. I rarely use voice and SMS so these flat-rate deals are usually poor for me!

Some test results in Bonn.
http://www.umpcportal.com/2009/06/3g...-vs-x70-vs-s5/