+1!
Practice getting your vibrato in-time with the metronome too. Start off slow (60Bpm) and do quarter notes-strictly in time. Move it up to 8th notes, 16ths...all the while keeping it in time. It really pays to work on your slow, wide vibrato. Sounds very expressive too.
Listen to other players. Mimic their vibrato and try out vocal phrases and use vocal style vibrato too!