A few years ago I've registered with a sipgate.de Karlsruhe phone number, which you can then use a sip / voip-enabled device. This then goes for example with the Fritzbox directly or with Android on Milestone by Sipdroid.
In principle, therefore, very useful to have a German phone number, on the one from Germany via Flat (most in Germany by now) or can be called very favorable, although the number over the net for example, Saudi Arabia "is derived.
Link quality
To the device, it is not the issue here. I have sipgate used here with the above-mentioned Sipdroid and Ekiga with Kubuntu and I must say that I am relatively disappointed. Basically, it works quite well. The problems show up in the detail. I had regular exposure of 2-4 seconds in both directions in the interview. Mind you, while the other continued to talk! In part, this was said then was subsequently confirmed in compressed form. Sounds at first may not be bad, but disrupts the flow of conversation immensely.
With Skype, however, to date, I had fewer problems. Clearly plays well with Skype's Internet connection is crucial. Here to comment latency or short interruptions in the connection is not interrupted in the conversation, but in delays. That is, you just wait longer responds to the opponent. Although not nice and you fall to the frequently interrupting each other, but still a lot more comfortable, so complete misfire like sip (gate).
Unfortunately it is currently very shaky anyway, so that Skype and Sipgate are currently either way not much. As well wait for help or just dig deeper in our provider Mobily ...
German phone number
Currently I have therefore to sipgate credit (which I have to charge it) and for several days even with Skype. The former I will be out in the near future, above. Reasons, use up, but not before. The latter however, the more quickly. Recently, it was not possible to sign on to Skype a so-called SkypeIn phone number for Germany. Meanwhile, the go back, but the cost of 5 € a month for simply providing the phone number prevails in our case is not on the benefits.
In other words, the moment I can only make phone calls using Skype to Germany, but Germany can not be called out. It is therefore a "anklingeln on the sipgate number can be" and to call back out via Skype. I also know of no way currently SkypeOut (then called the phone calls to Skype Out) to use on the milestone.
In total, therefore, somewhat awkward. On the other hand, we can doubt be called free and very cheap calls from Germany. In effect, therefore, to complain no reason 
