Idk about sequential, but on a normal manual straight cut gears I would see it as being pretty streetable. There were straight cut gears in the formula ford I autocrossed a couple years ago and i still used the clutch to shift, you don't have to , but I did most of the time because it was easier on the gear box. On the other hand I could not out shift the gearbox, whereas on the MR2 the gearbox does not shift as quickly as I would like it to without grinding. A dog box always seems to grind in some way when you are sitting stopped and put it into first, I could never put it in first without grinding it in some way.
Just a little info, not sure if it's on the right track, but that's my short experience with them.