Thank you everyone for the replies. It certainly helps a lot.
To netwolf:
I am after a ready made solution and David Ek's box requires quite a bit of soldering and I'm not too comfortable with that.
To acropolite:
I am not trying to compare the adapter to Argo Navis. I am just interested in an alternative to it.
These days it is nearly impossible to buy a laptop that has a serial port - mine does not have one. On top of that I already have a PDA (that also does not have a serial port) and I use Astromist on it that has a 2-star alignment and also N-star alignment then BETI seems to a better solution to me. Also if I carry a laptop with me all the time (which I do) then it makes even more sense to use BETI if I use a program like Megastar (that also has support for the encoders box). Am I missing something?
To madtuna:
I exchanged a few e-mails with Astro Devices and got good and comprehensive answers to my questions.
To everyone else:
What makes BETI attractive to me is that I tried Astromist and I like its numerous features and I could have it connected to my telescope to have a 'push-to' functionality as well. I quite like having a graphical user interface. Now if there will be a version for the iPhone then it will be even better
Best regards,
J.