Are gloves like that worth it? Very much so if that's what it takes to keep your fingers from turning blue and maybe even falling off from frostbike if you bike in weather that cold.

The only real way to know how your hands will react to the cold is to buy some gloves, and if they're not warm enough, buy something warmer.

FWIW, "something warmer" can be something like these:

http://www.sierratradingpost.com/p/,...nd-Women-.html

One or two pair of those under lighter-weight gloves can work wonders. FWIW, I was wearing two pair of those liners under a pair of Lous Garneau lobster gloves when cycling in very windy 12F weather last winter.