I sell quite a few of the all-hybrid sets, as well as many combo sets made of 4/5-7/8 hybrids + 8/9-up irons. If you hit a 5-iron less than 150 yards and/or are over a 20hcp, then the all hybrid set would be a great option. The biggest differences between the hybrids and irons are the trajectory and the forgiveness. The hybrids will launch several degrees higher than the iron of the same loft, and they are also much more forgiving on off-center hits. But I only recommend going above the #7 hybrid if you're hitting your 5-iron/hybrid 150yds or less, otherwise you might find you hit the higher lofted clubs way too high and they just don't go anywhere.
Just as an example, a few month back I fitted a senior golfer who was hitting his Ping 7-iron 120 yards total w/100 yards of carry and 20 yards of roll. I set him up with the Pinhawk all-hybrid set, and with the #7 hybrid he started carrying 130 yards with only 3-5 yards of rollout, so 30 yards more carry with a much steeper angle of descent which resulted in much less rollout making it easier to hold greens.