If they can't get a good sight picture, it's not the rifle's fault. same with the mag seating and getting beat with someone who spent less on a gun.
The only real downside I can think of is mag changes and barricades. Depending on the rule set you use, using a drum takes away 95% of the mag changes you will have to make. The other 5% being matches like MGM Ironman and clearing malfunctions. If there's one thing Desert Tech can do, its put a nice trigger in a bullpup. I love my SRS covert.