On the budget end, the M&P Sport's reputation is incredibly hard to beat. I don't think you will find a finer AR at a comparable price.
The FA and dust cover are things that IMO are nice to have but hardly a make it or break it proposition; unless you plan to use the rifle in extremely dirty environments the dust cover means little (and it pops open the moment the first shot is fired anyway). The FA, well, if you use it you're probably as likely to make a jam worse as stay in the fight.
Are Rock Rivers and nicer guns worth the money? Sure. Will the Sport be a bad choice. Heck no.