Haskell is lazy, which paradoxically means that its execution is sequential. In order to be truly liberated the execution order needs to be unspecified.
Lazy and eager evaluation are both sequential evaluation schemes, and are properties of language implementations, not of languages. Haskell is thus not lazy (nor is any other language). Rather, Haskell is a non-strict language, meaning that lambda is just abstraction, not abstraction-plus-strictification as in "strict" languages. Non-strictness does not imply sequential evaluation or indeed any particular evaluation order. (Ditto for strictness.) For instance, speculative evaluation is a parallel strategy that can implement non-strictness.
Although I don't agree that "lazy => sequential", what he/she probably means is that Haskell's lazy execution model sets constraints on program execution, in analogy to an imperative language, which also sets contraints on execution order.
Advantages of an unspecified execution order: more compiler optimizations allowed/possible.
Disadvantages: even harder to reason about. In fact, some functions may or may not terminate, depending on the whims of the compiler.
Termination (really, non-bottom-ness vs bottom-ness) is a semantic (denotational) property, independent of the whims of any correct compiler. Execution/evaluation order, on the other hand is an implementation (operational) choice. For an implementation to be correct, the termination or nontermination of generated code must be agree with the semantics of the language.