I'm a Native Instruments B4 player. As it's been too long since I've played an actual Hammond, I'll have to compare ORGANized Trio to NIB4 more than the real thing, except for a few details I happen to remember well.
The good news is that it's comparable. Other cheap or free VSTi's I've tried in the past don't quite reach that level.
Overall, it's an extremely lively and playable Hammond clone, and reasonably authentic as well. It correctly implements foldback on both ends of the keyboard. For example, as you go lower on the keyboard, at some point the 16' drawbar tone is replaced by the 8' drawbar tone, because with the 91 tonewheel set of all but the earliest Hammond models, there weren't enough tonewheels to go lower. This happens for other drawbars as well, and at the top of the keyboard too.
The scanner chorus/vibrato sounds very realistic as well. Yes, the vibrato is cheesy sounding -- just as it is on a real Hammond! The chorus is very lifelike and musically performs the function Hammond players love it for. OT's chorus is a little stronger than NIB4's: the C1 OT setting sounds like NIB4's C2, and OT's C2 sounds like NIB4's C3. I don't miss the subtler C1 on NIB4, though some players might.
I find the drawbar sound itself to be quite good, although there are too many overtones in the 16', and this interferes with the clarity of bell-like tones such as 80-000-0008. Instead, it sounds like an Hammond that's in need of a tune-up (a bit too much "leakage"). Some folks like their Hammonds that way.
There's another minor discrepancy between OT and a Hammond or NIB4. In the latter, the sounds all come from the same set of tonewheels. The 16' drawbar sound for C4 is the same sound as the 8' drawbar sound for C3. This is not the case for OT, where each drawbar has its individual tone. However, except for the 16' drawbar, they're all similar enough that this isn't an issue.
Another subtle discrepancy is that OT doesn't emulate Hammond "tone robbing". When you play a lot of keys at once on a Hammond, the total volume is considerably less than the sum of all the individual notes, due to the fact that they're sharing the same tonewheels and the way the summing network is designed. However, I find this less annoying with OT than I do on most synthesizer "B3" settings -- not sure why.
One of the acid tests for a tonewheel clone is a palm slide with fast Leslie and chorus on. On a Hammond, you get a lovely bubbling sound -- something that synths and older clones like Oberheim OB3 just don't get. Well, it sounds just great in OT, much to my delight.
Overall, the sound of OT is brighter than NIB4 (regardless of NIB4 tonewheel set). However, I susepct it's within the range of differences we find from instrument to instrument on real Hammond organs -- or at least, not too far outside that range.
I find the Leslie tube amp sim to be useful but not as good as NIB4's. I wasn't quite able to get the classic heavily overdriven Leslie "grind" sound on the low end that I can with NIB4 (and I don't find the NIB4's tube sim to be quite stellar, either). Perhaps with more fiddling I'd find some magic settings.
The Leslie rotating speaker sim is good, although not quite as rich in imagery as other rotating speaker sims, such as NIB4's or the one built into a Genesis3 guitar amp/speaker modeler. Nonethelss, it's quite useful and playable.
Most features are nicely configurable, including the ability to select MIDI controllers for popular functions on the GUI. More MIDI controller configurability would be nice, so that I could set it up to respond the same as NIB4.
I was unable to make it respond to MIDI Expression (cc 11) to control the swell pedal. No doubt with MIDIOX and the documentation I could get that sorted out, though.
To sum up, I don't think this would satisfy a die-hard vintage Hammond lover. Long-time players probably wouldn't be able to use identical drawbar settings from their favorite B3's. But for someone who's looking for a great Hammond-like sound on a budget, Organized Trio is an excellent solution and a prize.