I manage to climb just about any hill but slowly and only with great effort.
I got this 12-27 cassette as I through it would make climbing easier than the stock 12-25 cassette. It did, but not nearly enough, so I got an 11-34 cassette and mountain bike derailleur to handle it. The combination did the trick. I'm still no faster on the hills but this gearing definitely is easier on my legs.