This article from May, 2003 says the airbags were redesigned to prevent punctures but seems to imply time or funding was not enough to see if the new design worked:

The day Beagle almost died.
By Dr David Whitehouse
BBC News Online science editor
http://news.bbc.co.uk/1/hi/sci/tech/2950700.stm

These two pages show that the airbages used on Pathfinder were much more extensive than those on Beagle 2:

Airbags May Bounce Back to Mars
http://www.space.com/scienceastronomy/solarsystem/mars_airbags_000707.html

Arrival at Mars: The Beagle landing
By Helen Briggs
BBC News Online
http://news.bbc.co.uk/2/hi/science/nature/3304085.stm

The Pathfinder lander also used retrorockets to bring the lander to a complete stop in the air before it was released from the parachute to fall cushioned by the airbags.
Beagle 2 did not use rockets. Then the less robust airbag system had to absorb the shock of falling at a speed slowed only to that allowed by the parachutes.
The retro-rocket plus four-sided, multicomponent airbag system appears now to be a proven system with two successes.
Perhaps it will be used on the next European attempt to send a lander to Mars.

Bob Clark