I use two, which are the Antari S100's.
The output is excellent, indoors you can get snow blowing 30+foot away from the machine when its hung about 10ft up.
Unless you start mixing your own snow fluid from concentrates (mix with distilled water) then you get "snow" building up on any surface it lands on eg: Carpets, dancefloors etc. The snow is really tiny "flakes" of foam bubbles. When the foam clears/disolves/evaporates (whatever!) there is no residue EXCEPT on GLASS, it leaves windows looking like cloudy dalmation dogs.
The "trick" is...how long will the snow last (isnt it always the trick)? One of the big variables seems to be temperature.
I've "snowed" our front garden, driveways, trees, cars, porch etc, 2 years running now (on Christams eve, or boxing day...etc...whenever we're expecting visitors... With a snow machine hooked under each arm it takes about 10 minutes to cover the area to about 4 inches deep.
On both occasions the effect has lasted 2 days !!!! almost 3 days when the weather was colder.
In warmer outdoor events (like Christmas light switch ons in November) from the top of a 4 storey building, both machines ran continuously for 90 minutes (with hot re-fuelling of fluid...they use 5 litres EACH in 45 mins at max output)...the snow drifted all over the market place/square and even carried down wind along the high street 18 shops away!. The snow on the ground didnt really "settle" as there was too many people walking around. But certainly no slippery residue to worry about.
One thing to be aware of...unlike a smoke machine, their principle working part is a whopping great fan to blow the snow out. The fan is most definately (DEAFinately?) audible over any indoor music output (within reason)....unless you get it mounted several floors up, above the dancefloor. Not much chance of using it "subtle like" over the top of "White Christmas" at the end of each Christmas Party...