Poor on snow? I disagree. Different to a locked, limited slip diff car? Yes. Will most people notice the difference if they're using the correct tyres for the conditions and driving on treated roads? No.
Splitting the hair: the Haldex will by definition wait for some slip before diverting power. It's not a viscous coupling where there's always 5% of power going to the rear wheels, but it's more efficient as a result. It's not a synchronous system where 50-50 splits are the norm, like the Subaru, nor is it a Torsen mechanical diff which will be faster in pushing power around but also less efficient.
Having written all of that, I've been driving two different systems this past winter and the differences are shades of grey. They're both a world better than the FWD, spikes or no (all cars currently run Hakka 8 spikes in different sizes). What conditions? I've been driving to the office, which is now 400kms away, and we moved house from south to north, 300kms further north. I've plastered so much snow on the rear hatch that I've had to dig my way in to the handle to open it. Plate has been unreadable many times because of snow. I've put well over 16000 kms on the Superb in some varying, sometimes absolutely atrocious conditions, down to -28C, with regular snow and ice from October through to late April; I changed to summers again beginning of May and had winters on already in mid-October. I'm not looking for the ultimate in grip: I want something that gets me from A to B rapidly and without drama. The Superb pushes those buttons really rather well.
The electrical gizmos in my wife's Suzuki S-Cross mean that the Auto pushes too much power too late to the rear wheels, so it's unnervingly unpredictable. Setting to Lock and Snow mode - so power 50-50 and front / rear the same rotation rate - makes a huge difference and it's much more predictable as a result. The viscous coupling in the previous Swift was faster to react and better to a point, but in normal (even normal winter) driving, the difference is nigh-on undetectable unless you're looking for it. ESP on the Swift felt like it was reading your mind, the Superb's lets things get a little more lairy, the S-Cross and A2 systems just feel slow.
The Superb does a great job of shifting some power to the rear when it's needed and ESP an even better one of limiting the excesses of slides. My personal favourites are definitely the ESP Sport mode in the Superb and ESP off / snow / lock in the S-Cross. Both are eminently controllable with a sensitive right foot. Flick, destabilize, add power, sliiiiiide, dab of oppo, and we're good. Feeling like a hero at 20km/h I will be trying to push the Superb on the ice track this winter if we get an event set up, I really want to push the limits harder. But from here, as a long term winter driver being relatively new to 4x4 in its many forms, this is a game changer for stability and I don't want to revert to FWD.
There was a grand total of one time last winter when I actually felt I had to seriously slow down as the car was dancing. We'd had 10-12cm of snow at around -10C and it was essentially unploughed on the main road to Jyväskylä south of Suonenjoki. Speeds down to 60-65km/h and we were good. Further south, where the ploughs had been through, 80km/h was possible again. I'll repeat myself: Poor on snow? No. It's a stunningly good all-weather cruiser for long distances. I regularly do 250mile one-way commutes - so 800km in one day - and it's quiet, comfortable, and eminently capable, come rain, ice, snow or glom of nit.