So the first phase of tests at Jerez is over. Based on comments I have read so far the current Top3 arguably consists of Red Bull, McLaren and Lotus! Ferrari is a question-mark. It is very difficult to rate midfield, because many teams have managed to leave some impression there.
The Lotus situation is interesting. Basically they started out in a similar fashion a year ago. Renault-Kubica were immediately at the front in the first tests and were viewed as a genuine threat to top teams. Later in the beginning of the season they indeed got two podiums with different drivers. So let's see, how well can Lotus keep up development this year and how wide is the performance window of this car across different circuits. From that point of view Barcelona testing can tell us something more as it puts more emphasis on aerodynamic grip than Jerez.
The situation of Ferrari can be considered intriguing as well. But whatever it is, from the winning point of view it should be noted that if you want to beat a team like Red Bull, it is basically needed to perform flawlessly and you can't afford setbacks. So they have made their life difficult.