Nope, I don't think any of these are a criticism for a newbie.
A low price is never bad. It makes it easy to acquire. You don't risk a lot of money.
Actually, not quite. People have a sense of how much something 'should' cost. If you go too far under that, you risk giving the impression that your product is a piece of cheap rubbish.
And, when in a toy store, when presented with a more-expensive but quality product and a piece of cheap rubbish, a wise parent will always go for the more expensive option - it's less likely to break or get lost, and more likely to see some proper usage.
Going for the low price isn't always a good idea.
The too-short level range is not really a concern for the newbie - only for the guy that actually wants to keep playing the thing but is not willing to spend more money.
It is a mistake to expect people to play through the whole Red Box and then upgrade. The most likely time for them to upgrade is while in the
middle of playing through the set. If they reach the end, it's likely they'll want to upgrade for a while... and then they'll put the Red Box away and forget all about it.
If the level range is too short, they'll play through the Red Box in a session or two, and so go beyond that "upgrade sweet spot" all too quickly.
The slight differences in the rules don't matter for the newbie much, either.
Fair enough, this isn't an issue for the newbie. Although it becomes an issue if a prospective player goes into an FLGS and asks where to start, and the (experienced) players then advise him to avoid the Red Box at all costs due to the incompatibilities. It becomes an issue if a Red Box player sits down at a low-level 4e-Essentials game, or worse 4e-Classic, and his character doesn't quite work (the Pathfinder Beginner Box has the same problem with AoOs, FWIW). And it's an (admittdely very mild) annoyance when upgrading to the 'real' game.
None of these criticisms are crippling, of course. As Mearls has said, the Red Box was a success for WotC. But there are better ways to do a Starter Set, and they should be investigated. Simply dismissing these criticisms out of hand because "they come from experienced players" does absolutely no good at all.