I agree with the original post. Adding cards (especially ones that already exist in my inventory) is more confusing than it used to be.
One of the confusing parts is adding multiples of a card at once. As DoctorUgs said, when adding two copies of a card, it's much more intuitive to add both immediately (by typing the name then entering '2' for quantity) than it is to add the card to my inventory, then modify its quantity. It makes me feel like I have less control over the specifics of what's going into my inventory. Maybe I'll forget to modify the quantity, or maybe my internet will go out and I'll be stuck only halfway through, and have to remember to go back and modify the quantity of that card.
I don't like that the card auto-adds itself when I click on a card suggestion. I don't like that there's no Add/Apply/Save button (until after the card is added). Adding cards should be something I am sure of -- a black-or-white transaction that is either completed because I told it to complete, or not completed at all. I do not like being unsure about this sort of thing. It is not an auto-completed web search; it is a 100% accurate reflection of my card collection. I do not want the system to guess what I want to do when I click on a card suggestion even if it's right 95% of the time, because that other 5% is nerve-wracking.
For now I have resorted to the 'Card list' add functionality.
P.S. I also miss the auto-suggestion link reminding me to sort by 'Last added'. I always want to sort cards by that when I am adding, and without the reminder appearing, I often forget and start thinking that my cards didn't actually add when I don't see them appear at the top of my inventory.