I love the F100, but as JumboShrimp says, not really in Modern Times. In DOTM I currently have a fleet of around 140 of them and they're doing great.
The main downside I can see compared to the 737-500 is that the F100 is as big as you can go within the same fleet type, which could be a bit limiting unless you plan carefully (the 717 suffers from the same problem). Also, the F70 isn't all that great so you're really limited to a very small, niche family for commonality purposes. The Boeings and small Airbuses all cover a much wider size range within the same fleet.