Those of you unfamiliar with Renoise, it's first and foremost a modern music tracker product; it focuses on sequencing much like the mod tracker files of several 90s computer games, such as most games based on the original Unreal engine.
With Redux, however, it appears not only have they allowed their work to be used with other DAW's, it focuses less on the sequencing and more on the sound and sample design, which is probably why it's a bit more affordable than the full Renoise.
What probably attracted me the most to Redux in the first place is its and Renoise's multiple sample interpolation modes. It's the only solution I'm aware of beyond the quirky Waldorf PPG Wave 3.V that offers no interpolation when pitched down but also resorts to bandlimiting when pitched up. While the latter process is a relatively modern innovation in sound design, the result is not that different from the Fairlight, Synclavier, and Waveterm, which had higher playback sample rates than recording sample rates in order to attempt to control the high note aliasing for those systems. Such a sound I have yet to see implemented even in the recent TAL-Sampler.
Alas, every product has at least one drawback, and Redux is no different. The sound designing process is more technical and less conventional than one would expect for a VST. For instance, merely applying modulation to a filter is not exactly straight-forward because you use mathematical operations to combine everything, and even then, there is no parenthesis command I can find, which can make certain aspects of traditional sound modulation even more difficult to accomplish. The amplitude envelopes also do not have an exponential curve like for most other VST's; it's linear. Fortunately, I have heard that Renoise plans to address the latter problem.
I had had another quirk with Redux: its default instrument setting is monolith, meaning it copies every sample used into one file, and there's no way to change that from the VST itself if, for instance, you're tight on disk space. However, I did learn of an interesting hack that Renoise themselves informed the public of.
Judging from this post, I'm assuming it might be possible to trick the XRNI files into reading samples that are not inside the archive, though I'm going to test that theory later today and update this post with the results.
Regardless, kudos to Renoise for the interpolation modes, and provided one has a good technical and mathematical background, I can easily recommend this VST.