The tone but
especially the feel, and response is excellent. As others have said, the software is frustrating and clunky to use, but you get used to it in time, and I believe it will continue to improve. The user base is growing fast, so IK Multimedia will continue to invest in the platform.
I think for bass, a lot comes down to if you are wanting to play/record in a computer-based studio, or play out live (or both). Also, what sort of speakers/PA do you have to play through that can give you adequate low end? That would determine if you can use amp-only models played through your own bass cab. If you don't play out live, you don't really need the pedal and can just use the software in your home studio. (Or you could use something like Gig Performer on a laptop for live performance).
You can download the Tonex CS software for free to experiment with, but there are only two included "pre-loaded" bass-related tone models. One is an Ampeg SVT-CL amp+cab with the drive cranked up a bit, and the other is a Sansamp RBI pedal. However, you can also access all the ToneNet user-contributed tone models online (though there is "demo" white noise with the free version). As @seamonkey says, there is a growing collection of bass-related captures there, although the quality varies. Most of the online bass captures are very good to excellent.
For guitar, there are a few people who are doing high-quality captures using vintage amps and quality microphones, and selling them (usually at very low cost), and some of these (such as amalgamaudio) take the Tonex to another level. In time, I'm sure some will arrive for bass.
Here's a link to what tone models are "pre-loaded" into the various Tonex software versions, including the free version:
https://download.ikmultimedia.com/html/tonex/TONEX_Premium_Tone_Models.pdf