Very good synth, absolutely worth adding to your stable. Toxic Biohazard is absolutely perfect out of the box for dance, ambient, house and trance tracks. It stretches nicely to suit other styles, and is very easy to program and experiment with.
Since I moved to Mac/Live, I've been missing a strong FM sound in my palette. Toxic was a breath of fresh air. I had played around with Toxic II and III, and when I finally mulled it over and was ready to buy, this plugin had taken its place.
I was put off at first, because the presets I'd fell in love with on Toxic III seemed mostly absent. I found a forum post saying that the older presets were compatible with Toxic Biohazard, so I gave in and got it (and yes, the presets from the older version worked perfectly).
Also, there are a ton of presets you get when you buy which aren't in the demo. I had a little trouble downloading the preset packs, but I got quick and excellent support from the forums and also from the developer. Good show there.
The sound is crisp and clean in the mid to high end, and is capable of some nice warmth on the low end. Some of the sounds are extremely rich and often stunning. For all its sonic power, it sits nicely in the mix.
Another area it stands out is the pattern sequencer. It's easy to setup, has 64 steps, and you can copy your pattern to other patches (handy). The import doesn't seem to work with random midi files, and I wish it did. But I can see there would be some big technical snags with that, so I'm not sweating it.
The AU version seems to suffer from some minor issues with Live 6, and the developer responded immediately that they're looking into it. I switched to the VST, and have had zero problems. Again, good support there.