Here is a similar but still unique take on this subject.
I've fancied myself a guitar player all my life... problem is, I figured out many years ago that I have no rhythm (practically none). I still continued to collect instruments (including my wife having a 4 string Kramer Barretta 422s/p), a couple of electric drum sets and the like. I ended up being a sound guy for a local touring cover/original band for a while in my early twenties and got up and played on some simple songs and such for fun. I was also learning a bit of rhythm along the way. I've always loved and wanted a 5 string, every now and then putting out offers on craigslist for a bass here and there but never getting them (my offers were too low). So I only played them on occasion if someone had one or at the music store. Never with a band and always just noodling around.
Well, couple of weeks ago, I became a bass player (not really). I was providing A/V for a (book) writer's convention where a few authors always get together and play really poorly some cover tunes. A while back their guitar player wasn't going to be able to fly in so I suggested they hire a friend of mine who is an amazing singer/song writer guitar player. The gig went south and he took over basically doing his solo act and they fell in love with him. Now every year they hire him to play (he's the only one I mic so I have something consistent and good to give the audience LOL).
Well, this year, at 10am I get a text: "Hey, you should play bass tonight with the band." Clearly the bass player wasn't going to be there. I already knew the keyboard player wasn't going to be there so that had me thinking, "uhh... we will have ZERO low end now". But we don't have a bass as this gig takes place out of town. I'll call the House of Blues (where we were playing) to see if they have something. No answer. Then I remember, "Hey, my brother-in-law lives in town and he has a bass!" He's in Europe on his honeymoon but a quick few text and I'm off to his place to grab his bass.
A Spirit by Steinberger 5 string. Cool, always loved the Steinberger style guitar and bases and I'll have that cool low B string to rattle some fillings!
Order room service for lunch so we can quickly go over a few songs because I haven't even touched my guitars in 6 months and I really don't know any songs anyway, definitely not any of these songs! I mean, I know the songs from listening to them on the radio so I know the feel, but I couldn't tell you a single chord in the songs. So we get some chord charts drawn up. Thankfully as a kid when I first started playing ALL I wanted to learn was everything about music theory (yes, I was weird in that way). So I know what Cmaj7 is and all that and I know my fret board FAIRLY well at least up on the first 5-7 frets or so. I can fake my way through this for the night. It will be fun... I'll keep it simple, play some root notes... maybe even throw in a 5th or an octave here and there if I get comfortable.
Now comes the problem... That damn 5th string. For ~30 years the top string has been an E (or D in drop D).... my brain can't seem to remember this. B is E and E is A on everything I'm trying to play. I SLOWLY start to transition but quickly slip up quite often. Even when I decided I wanted to play a Low D at some point. I just hit an Open B because my brain said "Low D must mean drop D" LOL Oh, it was a struggle.
During the gig, I finally started to pull it together, still screwing up a good bit, but quickly catching myself.
The one thing that I did realize is that it's actually kind of hard to find the right place to put that Low B into the song. Like someone mentions, it sticks out like a sore thumb even when it's the right note. I started to find the right places but I thought I'd just be putting it everywhere and it would be cool. Not even close. You really have to be selective with it.
I still want one, and will get one. I'm just skeptic on the "need" for it for sure now and I don't know how much I will really play it. I fear of getting used to it and then having to play the 4 string again and go through a reverse of what I experienced that day.
Highlight of the story is that I played my first gig as a "musician" with a band at the House of Blues and even better... I wasn't the weak link in the band.
I also learned how important a good drummer is and how a bad drummer can REALLY cause some problems!
I've also been pretty heavy into trying to learn some bass and rhythm now. I'll never be a "real bass player" but at least I will be able to confidently sit in from time to time and I'm hoping every year that I get to play the gig instead of the family friend that they usually bring to play. He's not really much better than I am (his bass, Fender American Deluxe precision, actually has key notes taped on the fretboard... such a shame).
Sorry, that was a REALLY long post... but it was from a completely different perspective in a sense... yet still echoed a lot of what has been said about the transition as well as the use of the Low B.
Gilligan