In reply to nk:
I too went from playing the guitar to the uke and now have a soprano with G,C,E,A tuning and the chord shapes are the same as on a guitar, only 4 chords lower (forgotten the musical term for this) i.e G chords on a guitar = C on a Uke, , A=D, D=G. It doesn't take long to get used to it.
I have a "Vintage" uke, cost around £25, nice enough sound, though the more you spend the better sound you get!