Life seems to be a not-so-low probability event. Commonplace chemistry generates very fast all the necessary basic of our life chemistry. Then you have clay and the like that are extremely good candidates for creating self-enclosed biochemistry factories - protolife, in other terms. Plus, it looks like, in geological terms, life appeared on our world very, very fast, meaning it's either praticularly favorable, or it's easy.
Compared to this, the evolution of complex life (capable of massive data storage and mutation and all that) appears to be more unlikely.
So a significant number of scientists expect that "habitable planets" will be essentially giant bacterial mats, and nothing more.