However you choose to do a migration from drupal 6 to drupal 7 if you have any complexity in your site it is going to be ugly. Lots of errors and leaps of faith :-).
I choose to do it with drush. So after the drush made what it could do. I tested the site. Not working at all, not even logging in possible. What I did is:
1. Renamed the modules directory so that modules are not loaded. Then managed to log in. Then run update.php and put back all the modules. Then run some more update.php and enabled modules that were disabled and are new to drupal 7 but needed. Cleared some cache, cleared settings.php and removed some includes of FB modules that made errors.
2. Then I was stuck with garland theme and I installed fusion theme and enabled starter theme and set it as default and block settings were back from database (fusion starter was my default theme on D6 version) add your drupal 6 fusion css's, images. If you are doing it right, adding your local.css should be enough. If you have some customizations I really don't need to tell you to add those aswell.
3. I have multilanguage on site. So enableing of all the needed modules had to be done aswell as some configuration, especially part with path prefixes as it is differently done in D7 so you need to do it manually.
4. What about Imagecache settings, they are not imported so you need to fork them out. Go and make this http://drupal.org/node/1316472 run the number #4 in your drupal root and run it once. You will have them back. Ugly but works. (you can also download that file below)
5. CCK is now in core, but fields are not migrated. You need to install CCK once again, this time D7 version and use migration CCK module that is there. Go to /admin/structure/content_migrate (clear cache before) and then you will have interface to do migration of fields. Do that.
6. Taxonomy and views should be fine, but maybe you will have some broken handlers for taxonomy fields and some arguments, in drupal 7 they are called contextual filters. Not a big problem to solve.
Run update.php few times during this process, especially when enabeling modules and don't be scared of messages like "The website encountered an unexpected error. Please try again later." or some other errors, drupal will not lose your data, you just need to find a way to get proper configuration to get access to your drupal 6 data and make it drupal 7.
One note, many modules are now in core, 50 of them at least http://www.unleashedmind.com/en/blog/sun/more-than-50-drupal-modules-mo… I would find more that could be useful but ok, there has to be something done in drupal 8 aswell.