The bass solos I've had the liberty of playing live at shows usually have been the type (as said before) where everyone backs out and it's basically (pun intended) just bass and drums. They're fun and can be flashy, or not, it always sounds good.
I
love bass when it's the lead, but
only when it can hold down the low end at the same time (or has someone or something else to do so). I feel low end grooving matters more than anything, but if you pull off both at the same time, you're my hero and I'll most likely try learning some of your songs. lol
Also, I feel being lead in a song and doing a solo are two VERY different things.