"We have a lot of things to do and things to improve, but it's definitely a positive start and we have something to work with."
Ferrari failed to win a grand prix last year for the first time since 1993 and Raikkonen endured his worst season in the sport, finishing 12th overall and without a single podium appearance.
The team had three team principals last season in a major shake-up, with the most recent Maurizio Arrivabene arriving in November.
He has set a minimum target of two wins in 2015.
Germany's four times world champion Sebastian Vettel has arrived to replace departed Spaniard Fernando Alonso and lapped fastest in the first two days of testing, although times are less important at this stage than mileage covered.
Raikkonen, who did 92 laps equal to 407km on Tuesday, ended the day second fastest behind Brazilian rookie Felipe Nasr in the Ferrari-powered Sauber.
"You usually know if a car is good or not, and this year is a completely different story than last year as I had a good feeling straight away when I went out," said Raikkonen.
While Mercedes again completed the most laps, with Nico Rosberg doing 151 at the wheel on Tuesday, Ferrari's improved performance has been noted by their rivals.
"We are keeping an eye on the opposition, especially Ferrari has been an eye-opener in the last couple of days," said the German.
Australian Daniel Ricciardo, Vettel's team mate last year at Red Bull, agreed.
"The time Seb did yesterday was quick," he told reporters. "I don't know about fuel and tyres or whatever, but it was a good time. Ferrari looks good for now."
The season starts in Australia on March 15.
(Reporting by Alan Baldwin in London, editing by Toby Davis)
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