Upgrading Drupal

I just upgraded from D4 to D6 and need to "upgrade" my url format. New D6 sites don't create ?= urls by default like the D4 sites did. Before I flip the switch to clean urls, let me ask a stupid question.

If I turn on clean urls in the D6 site, will someone using my non-clean urls still reach the right page on my site? In other words, will someone following a link to http://example.com/?=node/1 reach http://example.com/node/1 ?

made update 6.7>6.9 and lost HP!
Now I looked many howto´s and read many descriptions to be sure but failed again.

1) backup
2) disconnected all modules
3) deletet all without _sides
4) uploaded 6.10 and checked settings.php (no changes necessary) info also copied.
5) update stopped. Second update.php start okay??
6) connected all module > updates needed > new modules uploaded
6) update.php started >>> errors! <<<

I don´t know what to to with the errors:

We are in the process of upgrading a Drupal 4.7 site to 6x. We have fixed many problems and updated functions and Drupal 6 is running and serving pages correctly, but we are having a lot of problems with blocks. As per the documentation, our .info file defines our regions, and the templates are printing out the regions correctly (I think):

in .info
regions[left] = left sidebar

in template
print $left

* user warning: Table 'xxxxxxxxxxxxxx.menu_router' doesn't exist query: SELECT * FROM menu_router WHERE path IN ('node') ORDER BY fit DESC LIMIT 0, 1 in /home3/xxxxxxxxx/public_html/xxxxxxxxxx/includes/menu.inc on line 315.
* user warning: Table 'xxxxxxxxxxxxxxxx.menu_router' doesn't exist query: SELECT * FROM menu_router WHERE path IN ('node') ORDER BY fit DESC LIMIT 0, 1 in /home3/xxxxxxxxxxxxx/public_html/xxxxxxxxxxxxxx/includes/menu.inc on line 315.

Why is the upgrading of Drupal core such a cumbersome and awful undertaking? Why cant I upgrade Drupal core like I do regular modules? Uploading and running update.php? As a result of that I am constantly behind with upgrading. I am talking about upgrades from 5.x to 5.y. I wonder whether I will ever upgrade to D6.

TR

How do I get configuration updates out to "pre-configured" sites? I'm currently using install profiles to "pre-configure" drupal sites, but they offer no way "re run" the profile on an existing site when a new version is released.