My IOD is what I opted for after selling my Alembic F-1X.
I wanted active tone controls (cut and boost), where the F-1X was cut-only.
In Dry mode, the IOD is a "clean" preamp. The overdrive function is VERY sensitive and changes significantly with slight changes in the balance between Wet and Dry signal. Twidding is involved to get it down.
Be sure to get the foot switch for Overdrive. They also offer a pedal that takes the place of the Overdrive knob, but it is pricey, and probably a waste of money. I do not own it, nor do I feel a compelling need to own it. I down the foot switch for Overdrive, and that is 100% required.
Output of the IOD isn't very high. You will need something in between to boost the output voltage high enough to drive a PLX to full power. The IOD only puts out 0.775v at wide open throttle. Spec came from SWR tech support, and practical use confirms this.
Tone is typical SWR. Sharp, clean, maybe sterile is also appropriate. Not sloppy or muddy.
The drive tubes will also drive an 8-ohm cabinet. If you have an efficient one (Eden XLT, JBLs, etc) you can make a lot of noise with just the IOD.