I've been using RealTracks since they came out, and have about 50 rendered to wav. There is a mix there, and we mostly play 'standards'. I have no problem coming in and out, picking up the horn, playing a verse on piano, her on flute or horn. I used to sing, but no longer, however. I don't have issues with the above.
Perhaps for simpler tastes it would be very easy to do a bass count 1 style, bass 1 and 3 style, then all you'd get is G nothing nothing nothing nothing G nothing...etc. The other would be counter bass as in G nothing C nothing G nothing..etc. That would drive me nuts.
I do find it odd that these bass players are 'overdoing it.' I guess I've gotta go hear Neil in Toronto again and listen to his group.
Here's a vid where he's playing with Terry Clark and Bill Mays, but I think he's on the solo only about 2:14 or so.
http://new.music.yahoo.com/neil-swainson/Midi bass lines can easily be done, then the edit/freeze thing can be done. In a group most bass midi is ok. Gives you the ultimate solution as long as you have a good synth you should get a really good sound.