One decision means you get one minute for that decision. If I play an EOT Gifts, I get one minute for my choices. If I play Tezzeret's search ability, I get one minute. Do players often take longer, especially with complicated gamestates? Of course. Is it entirely reasonable for an opponent to ask you to play faster? Yes, if you're taking more time than you are allotted. When I'm playing incompetently (for example, at the last Xtreme Games tournament) I frequently take longer, sometimes much longer, because I have no idea what I'm doing or what goal I'm working toward, especially with a deck I'm unfamiliar with.
I have heard this line over and over in real life and I hate to tell you, but the magical 1-minute decision is not true. The base-line for slow play is playing at a pace that would deny a player an equal share of the match time. In this case, if a player is taking 1 minute to make each decision possible, that player is actually very likely to get slow play warnings and potential upgrades if decisions aren't made timely. As with all rules, there are moments where a tough decision is to be made and players are allowed to take some extra time, but taking 1 minute to make a decision because one feels they are entitled that one minute is treading on a line that is bad for competitive Magic.