In reply to Tringa:
My Mum's had a similar positive experience with PPs after breaking her femur last winter. It's honestly made the difference between being able to walk the dog twice a day, or not.
Aside from helping people with compromised mobility, I've heard nothing but positive reports of the design from anyone who's ever used them. They're 100% my preferred walking pole, and I find them especially good for long distances because they're so efficient and give you extra propulsive power and less wrist stress. The ergonomic handle is streets ahead of any other design I've seen.
The only downside is that they're less packable for winter climbing than a conventional ski pole-based walking pole. But in all other respects a normal pole is far inferior.