For years I put up w/ bad bass lines generated by the style I selected, and lousy rendering, totally different from the sound of an acoustic bass. I thought I had a solution w/ Real Tracks, but even the great sounding Real Tracks w/ the jazz bass (Ray, etc), have a built in restriction, and it is a big one -- you can't edit the bass lines. You are stuck w/ the generated bass lines. For many of you, that might be fine. I'm a jazz guitarist and I like to use only bass and Real Drums as a background for traditional straight-ahead jazz classics. Much of the time the auto-generated bass lines are not good. In fact they can be down right irritating. Maybe I'm too particular. If you listen carefully to auto-bass lines, you'll notice many times the notes don't carry a concept from one group of 2 or 4 measures to the next. So it might sound good for up to 4 measures, then it randomly starts another idea without regard to the previous few notes. That drives me insane. It's like listening to a schizophrenic. So what I have done is to take the trouble of inputting my own bass lines into the soloist channel, or modify some bass lines from a non-Real-Tracks style which I copy to the soloist channel. To get that great acoustic bass sound I use a plugin called NI BandStand. My savior! You can buy it through PGmusic or save money and go elsewhere. It operates either standalone or as a DXI plugin for BIAB. I use the DXI. It can be used to render all instruments, but I just use it for bass. It takes the bass lines in the soloist channel as input and uses wave recordings of acoustic bass and puts them all together. It sounds great, just like an acoustic bass, except slides and slaps are missing. I can't mimic the slides, but slaps can be somewhat faked by using clusters of bass notes w/ different durations, a slightly cumbersome process. I used to use BIAB's Roland VSC, but the acoustic sound from VSC is pitiful in comparison to Bandstand.

The bad news -- it take me 1-3 hours per song.
The good news -- the result is fantastic, and if I don't like the bass, it's my own d...m fault and I can change it.

If you have the time to do your own bass, I highly recommend getting Bandstand w/ BIAB.