There will always be missed or blown calls but with these refs they're extreme. Most of the time you can argue it both ways. However these refs are just missing things that are obvious and even on replays they get it wrong. Cobb's TD return for instance when they picked up the flag for block in the back. They may have called the wrong person for it but then in the replay there was an obvious one. On all scoring plays the entire play is review able and they missed it again.
The entire play is reviewable... but they can't call a penalty that they didn't call before. Otherwise, on almost every reviewable play they could probably call "holding" on a lineman... and they don't want to get into that can of worms.
So... review replay has never been able to result in a flag that wasn't dropped being dropped.
So, if the refs screw up and call it wrong... replay can't be used to do anything but pick up that flag... it can't be used to drop another flag elsewhere.
That doesn't defend missing the block in the back... just explaining how replay can't fix that kind of mistake.
This happens a LOT, even with the regular refs.
So... my grading of the replacement refs has a lot to do with how they perform based on comparison to my memory of regular refs in the past.
Remember the regular refs make a lot of these kind of mistakes too... and games have been lost.
As for picking on stupid ref mistakes... Remember a few years ago when the regular refs screwed up the coin toss in an overtime game? The ref got the call on a coin toss wrong! That's about as silly of a mistake as you can get... and I didn't see anything on that level with the replacement refs this weekend.
Yeah, they goofed a lot on the pre-season... but they cleaned all that up it looks like to me.
I actually think the NFL should cough up the money and pay the regular refs... but all things considered, I can't argue that these replacements did a bad job.