yes.... I used to play guitar and sing, and doing it on the bass is quite different than playing guitar and singing. with guitar you don't need to hold a groove down (well, not on most songs anyways) and can get into a rhythmic pattern that is easy to sing with.
the bass is different. you have to groove with the song all the time or it sounds like ****. It's like every song is as difficult to sing and play along with as say... the tragically hip's song so hard done by (which is a real bitch to play guitar and sing along with).
http://www.youtube.com/watch?v=0vHEV3llaHY
sorry to have gotten off track... what I have found is that you can take Sting and his music (the early stuff anyways) as the working model. the bass lines are not boring, they are quite groovy in parts, and easy to sing with. but overall not terribly complicated. it is more with less in a way. If you want to play really complicated bass lines and sing - good luck! hope you can pull it off, but almost nobody can really do it well. but a simple bass line that you can groove to the drummer and still sing is perfectly doable.
less is more. be groovy with fewer notes. you'll sound just as good playing the bass (even better probably) than playing too many notes. which reminds me of Amadeus (the quote "too many notes") anyways I'm rambling, but I'd say if you can't write an interesting bass line with fewer notes, you should learn.
or take trip on the wilder side: play chords on your bass when you sing. rock chords (first and 5ths) sound wicked on the d and g strings (and ok on the a and d strings). 7th chords minor and major sound great on the a d and g strings. You can bounce between the e string and a chord for variety, or play a small fill and finish it off with a few strums of a chord. then you don't need to worry so much about playing lines, and still cover the sonic bottom of the song.