Rhiannon had a big popularity surge in the 80s in Wales (where I'm from), so there are a lot of young adult Rhiannons about, and it feels quite unexciting to me. But it's a nice enough sounding name.
Similar-feeling names that are pronunciation-friendly for the non-Welsh:
Mared,
Sian,
Bethan,
Megan,
Gwen,
Carys,
Cerys,
Anwen,
Seren