Agreed with simultaneous play. We avoided it for a long while, then had a 7 player game and didn't have enough time to play at the game store we go to. Should have tried it much sooner! We'll probably never go back now. 7 player game took 2.5 hours.
I'm not particularly keen on the primary player only getting to research. That created situations more than once where players could take one more action--research--but had to take two (or pass) because they weren't primary. Surely there's a way to let the primary player OPT to research first, then the secondary player may choose to do so, so that there is no conflict. That was our only objection.
When we play we allow anyone to research, but if there's a conflict where the players with the pink and grey markers want to both research the same thing and there is only one, the pink marker has priority. Haven't really ever had any problems from this, especially when also using the second-player-to-pass-decides-rotation variant.
I should also note that we don't allow someone to just sit on their action and wait for the second marker to catch up. If one starts to catch up we wait for the paralyzed player to get on with it and for both markers to be on opposite sides of the table (more or less) before continuing.