I've used Aquila uke strings for years, ever since a friend recommended them for a cheap uke I got for my birthday. They instantly improved the tone and intonation and when I got a proper tenor uke a few years later I kept using Aquila strings.
They have a beautiful tone, and mean you can use the uke as a real instrument, rather than just jam and think that's all a uke can sound like. They are long lasting, though of course you have to change them eventually!
I must say I've never felt the need to try any other type of strings for my ukulele as I am so happy with these. Been using them for years and will keep buying them.