"They seem to be the lightest adjustable poles I can find, but read a couple reviews of the locking mechanism not working?"
I used the REI Peak UL Compact poles for several years and had occasional problems with the locking mechanism slipping. That was not enough to make me ditch them. The final straw was when one of the locking mechanisms detached itself from its pole section while locked in place in the next section. Not only could it not be dislodged, but it could not be replaced by gluing another one in. Come to find out, the expanders were not replaceable, so if they wear out or come loose while locked up in a pole section, you're SOL. Hopefully they have changed the design in the last 2 years, but it's definitely something to check out before buying. Just ask the sales guy how to replace the expanders if they wear out and see what he says. Meanwhile, I've gone first to Titanium Goat AGP's and now to
GG LT4's. The Goat poles were a big improvement, but almost as finicky as the REI Peak UL's. The GG LT4's are far and away the best poles I have ever come across for 3 season use. But I'd go with an external locking mechanism for winter activities to avoid potential expander slippage problems at "inconvenient" times due to water working its way up the inside of pole sections. I had this happen with the Peak UL's on a couple of occasions.