Is it better to learn Drupal 7, or Drupal 8?

A quote from one of Dries' blog posts (posted on June 14, 2011):

I think 18 months gives users plenty of time to enjoy Drupal 7's productivity at its peak before facing a possible update. At the same time, it's short enough that developers won't get bored.

UPDATE: Dries in an interview with CIO.com on Jan 4, 2012

Buytaert may have these plans for what he wants to see in Drupal 8, but the release date is yet to be worked out. "I would say Drupal 8 is probably, and it's a big probably, maybe two years away," he says. The release date will be determined in part by the continuing transition of organisations and developers to Drupal 7.

"What we're doing with Drupal 8 is we're tackling a number of big problems, so I think we want to release Drupal 8 when two things happen: One [is that] Drupal 7 is the de facto release; everybody is using Drupal 7 instead of Drupal 6 or Drupal 5.

What makes you think that?
You won't be seeing Drupal 8 for at least two more years. Have fun with Drupal 7.

Based on quote it is a no brainer to learn Drupal 7, however might also be beneficial to learn Drupal 6 and therefore have a broad knowledge of upgrade paths etc.

Drupal 7 is the stable branch for the time being. Regardless, this was the same situation I saw coming from Drupal 6: if you're going to go with the newer version, you probably won't get as many modules. You'll probably go from project page to project page and a lengthy open request thread on each page asking about the D8 Port, and when that's supposed to be coming out.

In short, it won't kill you to wait and use D7. It was a massive improvement over D6 in many respects, and most of the modules worth using have been ported over by now (save for a few that I really wish would've been done by now, such as Facebook-Style-Status-Updates, but I digress).

Anyway, dive in and have fun with Drupal 7!

Regardless of the version and cms, You should learn that what you actually need and use. There is no reason to learn something that will probably kill more of your time than bring you results. first of all, you should check your needs and than the abilities of any program, language, cms etc. as already said the newest system is sometimes badly supported because there are not enough maintainers, the search of the modules can get tricky and bugfixing is a matter of longtime exploration.

I know this is an old topic, but it's still a bit unanswered and the debate here isn't to use Drupal 6 or Drupal 7, it's whether Drupal 8 is close enough to consider waiting for it. It wasn't a few months ago, and it still is not anywhere near release. I think that the general community around Drupal, including people considering building a site with Drupal, is more aware of what's happening with Drupal 8 development than when Drupal 7 was at a similar stage of development, so perhaps there is a greater anticipation that Drupal 8 is "close to release" than there was almost three years ago (at a similar stage after Drupal 6 came out and when Drupal 7 development was underway).

What you should know is that Drupal 7 is a good place to start right now and while migration to Drupal 8 might not be easy, it also might not be necessary. Yes, Drupal 8 will bring some great new features... but do you really want to wait so long (maybe 2 more years from now) to begin your Drupal project? And even when Drupal 8 is released, it's unlikely it will be as ready for use as Drupal 7 is. It's taken most of a year for many of the most important contrib modules to be stable on Drupal 7. And with many of the changes going into Drupal 8, it's unlikely to be released with fully stable contrib modules, so you are likely looking at 2.5 years before you would really want to consider building very complex new sites on Drupal 8.

Back to the original topic... if you do get deeply involved in Drupal and the community, you can start being active with Drupal 8 ("learning" it) and help with its development while you work on your Drupal 7 sites. Then you will be more ready when Drupal 8 is actually ready for release and you will have been a part of the contribution process that drives "open source".

For more information about Drupal release cycles, see the blog post Dries wrote a few months back: http://buytaert.net/how-i-think-about-drupal-release-date-planning

I didn't see it posted, but you can't just wait for Drupal 8, you need to wait for all the contrib modules to catch up. So it's not two years away, its at least 3 depending on what you need.

I think that it's now better to get started with 7 instead of 6. Even if some modules aren't stable enough, most are.

In my opinion, it would be a waste of time to learn drupal 6.

The reality is that Drupal 7 and Drupal 8 are still very similar. The reason is that most of the patches that have been made, have been bug fixes, and other such improvements, which have been committed to both Drupal 7 and Drupal 8. I haven't really kept track and there are of course some changes between Drupal 7 and 8, but those changes are only just appearing now as the development for the new features in Drupal 8 begins.

When making a decision to learn 6, 7 or 8 it its worth looking at the usage statistics http://drupal.org/project/usage/drupal.

Drupal 6.x still has 200k+ visible sites that still use Drupal 6.x. However from current contrib module compatibility its clear that the best thing to do with a new site today is build it with Drupal 7.x.

There are still some widely used projects like http://www.openatrium.com, http://www.http://managingnews.com, etc that are a long way from even getting a Drupal 7.x upgrade. So it will depend on the type of work you plan to do.So if you get asked to upgrade a Drupal 6.x site or modify Openatrium you will have no choice to learn Drupal 6.x.

If you are only building new sites start with Drupal 7.x, Drupal 8.x will not be as high learning curve coming from 7.x since you will use things like entities etc.