"What does it cost? - During the beta period Skype is free and helps us to refine and improve our product. Eventually, some features and services of Skype will require a paid subscription or prepayment. Our ambition is to keep the basic functionality of Skype (PC to PC calls) free. More information will be provided once our beta program is complete."
To check out their full FAQ, click here. This program looks promising.
"They say it works despite firewalls - so can it piggy-back viruses, I wonder?"
Again, if you look at their FAQ:
On their 'What is Skype?' page, they also inform you:
"Works with all firewall, NAT and routers ? nothing to configure!"
Which means it will work with standard ADSL accounts which work over a NAT configured router.
Although, they do say this on proxies:
"Does Skype support connections through proxies and authenticating firewalls? - Currently, Skype does not support proxies or authenticating firewalls. Stay tuned for more enhanced features in the future."
Hmmm.... I am not sure where you got the immediate idea of 'piggy-backing' viruses?! A bit of paranoia is kicking in there. :-/ A fully updated Adaware reports no foreign objects. :-)