There should actually be two Ls in the original form of this name: Súilleabhán, Ó Súilleabháin. The second L comes from the D in _dubh_, for what it's worth: _súil_ 'eye' + _dubh_ 'black, dark' + _-án_ (a diminutive ending). [noted -ed]
Always been sort of neutral towards it, as it's my surname. However, I think it's a bit heavy sounding, and not really all that fit to be a first name.
Ua (Ó) Súileabháin : Clann of the White ("Blind") Eyed One.
Spelling may vary.