Is it worth to switch to InnoDB? Is it worth to switch from MyIsam to InnoDB for a Drupal 7 site that has 2000 visits per day? Would it be worth if it has 10000 visits in the future?

How much faster can a site become with InnoDB if it has mostly reads and not writes? And how much if it has a lot of writes in the database?

I'm asking all this because some articles I have read are negative about InnoDB, and opinions are split.

So, does the generally spoken statement "InnoDB is better always" reflect reality?
The general rule of thumb was to use InnoDB to write intensive tables (due to its row locking nature) and MyISAM for the read-heavy loads. I have seen a few very busy sites fully on InnoDB running without any hiccups or drop in performance too.

Drupal 7 defaults to InnoDB as the database abstraction layer has been rewritten and immensely improved.

You could look into MariaDB which is a drop-in replacement for MySQL, faster and has extra engines. There is also Percona, another high performance replacement. They both address some of the downsides of InnoDB.

The reason I am listing the alternatives is that Oracle made a few very suspicious moves and it may be that pretty soon we won't be able to use MySQL for free. (see http://arstechnica.com/business/news/2011/09/oracle-may-fork-itself-with-recent-mysql-moves.ars)

If bigger changes are not viable/possible, I'd recommend making a clone of the site using InnoDB and load test it using tools like Apache Benchmark, siege, New Relic