We have migrated a few servers from Raq 4's to Ensim Pro on Linux. The results vary depending on the complexity of the site.
We use a migration script to move sites, users, passwords and emails over to ensim. MySQL has to be moved manually. I am not sure about mailing lists as the servers we migrated did not have any.
Ensim uses a different filesystem so hard-coded paths in scripts may need to be changed.
Ensim has varying security levels that may impair some scripts requiring adjustments to the scripts permissions or lowering security for the site.
Usernames starting with a number fail to migrate.
MySQL database acccess may need to be changed to use 127.0.0.1 versus localhost in some scripts.
During a large (~1000) user move, about 20 passwords failed for unknown reasons.
Note that versions of PHP and PERL are different and may cause problems for some scripts.
ASP is not provided by default on Ensim.
Custom DNS setttings will need to be re-entered. The migration script does basic DNS.
IP based sites may be created as named-based sites and then later switched.
Some fontpage users had problems and had to republish their sites.
The time really depends on the complexity of the sites. Static HTML sites are not a problem. Dynamic sites with custom scripts and databases present a greater challenge. Each domain adds a few 3-10 minutes to the process.
Overall we have found the migrations to be sucessful and the people who migrated happy with the results and added features of ensim.
Some end user issues is that on named based sites on ensims, your users will need to use "firstname.lastname@example.org" as their login not just "username". The latter is due to the chroot filesystem in Ensim (which allows for identical usernames on different domains). This issue can be avoided by creating the site as an IP based sites.
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