vonage's softphone vs other soft phones

Archived from groups: comp.dcom.voice-over-ip (More info?)

i'm wondering why i shouldn't be able to hook the vonage adaptor up to
my modem and use any softphone out there (i used callsoft & callclerk
prior to subscribing to vonage this morning). i haven't received my
linksys adaptor yet, and am anxious to see if it works, since they
don't say a thing about using softphones on vonage.com.

i just want speakerphone. and unless i get speakerphone POTS hardware,
vonage doesn't indicate whether you can get speakerphone service with
their product.

anybody else out there that has tried this, or some other
configuration? i refuse to pay them 9.95 a month just to use a
softphone. isn't it the irony of it all, getting telephony over IP,
and having to scramble for some software to use it.