Within itself, this Codex is great. Fantastic internal balance, lots of seemingly solid choices, good spread of special rules without being overly complex or silly. Reasonable or good statlines for most things. Only a couple of units that feel over- or under-costed relative to their 'rivals' in the Codex, or to the baseline rules themselves.
The problems for DE start, however, when you begin to compare across Codexes to what other races cost for what THEY can do, especially to your vehicles...but this isn't their only flaw.