A 26-13 victory over Samoa was followed by a disappointing defeat to South Africa but the manner in which England played throughout November won plenty of plaudits.
And Johnson, who skippered England to World Cup glory in 2003, six years after he led the Lions to an historic series success over the Springboks, is happy with what he's seen from his charges.
"This time last year, Dan Cole, Ben Youngs, Chris Ashton and even Courtney Lawes weren't nailed on to start for their clubs. Now they've come off a run of six tough Tests against the best teams in the world and they're starting to understand what it takes to play at this level," said Johnson, whose team drew a two-Test series in Australia during the summer.
"I'm looking forward to the Six Nations. That will be a heck of a series as it always is.
"Seeing how quickly this team has developed in the last year, it can develop equally quickly in the next year."
Just six months ago, England's 2011 World Cup chances were being written off but their recent wins over the Wallabies have shown they are more than capable of beating the best.
Saturday's loss to the Boks reminded everyone just how much work England still have ahead of them if they are to match their final appearances of 2003 and 2007 but Johnson believes his men are now far better equipped to mount a challenge than they were a month ago.
"Whether that is enough for the World Cup, we'll see when we get there. In my experience you only win it if you get into one game and that's the final. We'll worry about it if we get to the final," added Johnson.
"There are seven or eight teams who can beat any side on their day, but what you want is for that day to be more often than not.
"This is definitely a far better team today than it was on November 5, the day before we played the All Blacks, in terms of our understanding of what Test match rugby's about. We have a very good squad which is very competitive."