Porteus

What are the major differences to expect when changing from v09 to v1.0-rc1 ? Can I use same modules or need to change them to xzm format ?

Compression changed.

If you click on lzm - it whould convert to xzm

Many of the major differences were outlined by brokenman in this thread: http://forum.porteus.org/viewtopic.php?f=53&t=472

Right out of the box, you'll notice that there's a new installer that has more features (read the install guide from within the installer, support for EXTLINUX, prettier windows installation, more foolproof to ensure the right drive is set up). Once you start booting, you'll notice that drives formatted with a windows filesystem can no longer used posixovl to store changes. This is for two reasons: 1) posixovl was highly prone to corruption, and 2) a bug surfaced with posixovl that made it incredibly slow to use, or it caused bootup to fail altogether. a save.dat is now created during bootup for users with windows filesystems. Users will need to manually update their porteus.cfg to point to the .dat container they create.

Next up is the upgrade to KDE trinity (32-bit) or 4.6.3 (64-bit), and the use of xzm modules in place of lzm. In the 32-bit version, you can double click on an lzm module to convert it to xzm.

Plus, lots of new CLI tools; some of the CLI tools from V09 have GUI versions now...lots of bugfixes, etc.

There have been substantial changes as compared to the v09, most notably the lzma2 compression. At least for the first official release older lzm modules will be automatically converted when you attempt to activate them (32bit)

Please see this thread for a more comprehensive list of comparisons.
http://forum.porteus.org/viewtopic.php?f=53&t=472

You may also want to try the rc releases which are ready for download now, and will be very close to the official v1 releases.