Enter the IT-1220 into my world about 12 years ago, and later the Equi=Tech system that does the same thing with more outlets.
Balanced power supplies and isolation transformers like the IT-1220 (I had one for years) and the Equi=Tech supply I currently use in my studio are designed to do two things:
First, isolate the incoming AC completely from the incoming power line and thereby eliminate outside noise, and;
Second, to create a Balanced Power Source that reduces hum and noise in a studio system by working like a balanced mic line or humbucking pickup: the two legs of the AC line are out-of-phase 180 degrees, thereby cancelling induced hum and noise from things like power cords on your studio gear that might otherwise be radiating into your signal wiring, etc.
All things being equal, this should reduce the noise floor of a studio by about 8-14 db, and I measured about a 10 db improvement in my system when I first installed my IT-1220 (I got a larger AC system later on, which is why I don't use the 1220 any more).
So Hans had and heard the results with a correctly wired studio operating on balanced power, and that's a good thing!
HOWEVER, balanced power has NOTHING to do with pedal or other equipment ground loops, it will not solve them, nor is it designed to, and it has nothing whatsoever to do with guitar pedals. Zero.
It does not take the place of a pedal power supply with isolated outputs for pedal power.
Understand that the thing that causes noise on most guitar pedal boards is simply the existence of ground loops, and this is because most pedals have different grounding schemes, and are inexpensive and not designed with big time power supplies built in that would require AC cords, etc.
The reduced noise floor inherent in a balanced power system is for studio gear, primarily gear equipped with 3 prong grounded plugs, and is NOT intended or designed to prevent problems caused by the typical guitar pedalboard wiring systems and various ground loops.
In fact, most studios using balanced power STILL make use of proper grounding techniques, such as star grounding and so on. I'll repeat: balanced AC power and advanced filtering do NOT solve ground loops!
In other words, these boxes do NOTHING for your pedals, in the sense that you still need to wire the pedals properly and isolate their grounds from EACH OTHER to prevent ground loops.
This is what a proper isolated pedal power supply will do.
But there is no doubt that the balanced AC boxes like the IT-1220 work and work well FOR THEIR INTENDED PURPOSE. And that purpose is not to isolate ground loops, it is to reduce the hum and noise radiated into adjacent signal cables from AC cords, etc, and to isolate the outside AC from your studio.
As for the rack mount "power conditioners." let me explain their very different purpose:
These were originally marketed because early digital gear was very, very susceptible to spikes and surges that would scramble their digital memories. A small brownout or power surge would literally crash computers, de-program synths and digital boxes like my old Eventide Ultra Harmonizer and TC M5000.
And so two kinds of "power conditioners" were used: The first and more expensive ones regulated the current to a degree so you'd get a standard 120V. The second was merely a glorified surge protector.
This was needed somewhat in the old days, if you gigged or had a studio in an area subject to AC problems, BUT modern power supplies on computers and digital gear are much better and these "power conditioners" wind up being truly unnecessary. If you have old (by this I mean 1980s or 1990s) digital gear in a studio, they might be a good idea.
Also, unless it's very well designed and manufactured, a surge protector's EMI/RFI filtering can actually add noise. My studio tech demonstrated this to me on his oscilloscope.
In any event, these boxes do absolutely NOTHING for guitar pedals. The do not isolate your pedalboard's pedal power outlets unless they are made for pedal boards AND have individually isolated outlets FOR EACH PEDAL.
I hope this explanation is clear, and helps.