It is my favorite by far. Even if my second favorite, the SilverGen were priced the same instead of being much higher I would still buy the Silver Puppy to make my own CS with. In fact, I would use it to make commercial CS too and may very well do that in the future, perhaps having a premium line that mixes Utopia Silver's advanced CS 50/50 with the Silver Puppy.
Don't believe the blue people scare stories - they are almost 100% bunk when it comes to applying to properly made colloidal silver. You would have to consume truly huge quantities for a long, long time to even begin turning blue, and the condition is reversible even if you did so.
I take CS almost all the time and have for a good year (except for a couple of weeks recently when I was out of town). Sometimes when it felt like a bug was coming on, I have had half a bottle or more per day. Recently, when I returned from out of town I caught that nasty bug. Half a bottle or more a day for a week and it was gone before other people's similar bugs who had it before I did.
Never a hint of a tinge of blue.