I won't bore you with the details of the package versions included in Squeeze, since I'm assuming that if you run vanilla Debian, you'll be smart enough to figure that out for yourself. The most interesting aspect of this new release is that it is the first to include support for FreeBSD - a project known as Debian/kFreeBSD, in both 32bit and 64bit. This means the Debian userland running on top of FreeBSD.
"These ports are the first ones ever to be included in a Debian release which are not based on the Linux kernel," the press release states, "The support of common server software is strong and combines the existing features of Linux-based Debian versions with the unique features known from the BSD world. However, for this release these new ports are limited; for example, some advanced desktop features are not yet supported."
Another very important aspect is that of the removal of problematic firmware blobs - which were non-Free code. These have all been removed, restoring the purity of the Debian distribution. You can re-enable them from the non-free repository - where they belong for a distribution such as Debian.
"Another first is the completely free Linux kernel, which no longer contains problematic firmware files," they explain, "These were split out into separate packages and moved out of the Debian main archive into the non-free area of our archive, which is not enabled by default. In this way Debian users have the possibility of running a completely free operating system, but may still choose to use non-free firmware files if necessary."
Debian runs on anything (Intel IA-32 (i386), Intel EM64T/x86-64 (amd64), Motorola/IBM PowerPC (powerpc), Sun/Oracle SPARC (sparc), MIPS (mips (big-endian) and mipsel (little-endian)), Intel Itanium (ia64), IBM S/390 (s390), and ARM EABI (armel)), and you can obviously upgrade your existing installation painlessly.