I'm in three RSO leagues. I think its a great set up. The rookie draft issue above is easy to correct, we let the system autodraft the rookies then I just removed the players from the rosters before the auction. I didn't find the live scoring to be all that bad last year, maybe a few minutes of lag time at its worst, but seemed pretty close to real-time last year.
Couple of knocks:
I feel like your leaguemates really need to be able to conceptualize the contract value and the player, or trading can be kinda difficult. For example, in one of my leagues, our bottom team has no cap room this year and 2 really bloated contracts. He can't seem to get past the concept that David Johnson at 2 years, $25mm for Michael Thomas for 3 years, $3.5mm is a somewhat even trade (he only has $2.5mm of cap space left and no WR1s on his roster).
The site also doesn't allow you to pass on rookie contracts, so sometimes you're stuck with your third round rookies on 4 year contracts because you were forced to pick someone (we're working around that in my other league by allowing managers renounce the pick and take someone that wouldn't be drafted). You can strike big (Dak last year on a 4 year contract worth $850k/year), but you can also wind up with Dri Archer and if you want to cut him in year 1, it's a $2mm cap hit.
They could better advertise the waiver players, if someone gets cut, you get a chance to pick up their contract before they hit free agency, and its hard to navigate to that location.
Other than that, I've been in RSO leagues for three years now and it's a great format if you're looking for a different kind of challenge in your fantasy leagues.