Hello.
If you're posing the question "Is it worth it?" in the first place, probably not.
Worth upgrading from an '08 8-core? probably not.
Worth upgrading from an '06 quad core? depends.
Worth upgrading from a G5? probably!
The '09 quad core is going to take a lot of heat for being "worth it" because every armchair general out there is going to compare it to an i7 homebuilt.
Which it is not. It is a Nehalem XEON-based workstation with an outstanding layout, great acoustics, solid case, a powerful and stable power supply and a lot of time spent getting the details all sorted out.
The '09 8-core is a dual socket Nehalem XEON workstation board with two quad XEON CPUs, six channel memory, an outstanding layout, acoustics, case, power supply, etc...
Both variants can legally run OSX (as well as Windows or anything else) if that's important to you.
Both variants are solidly built, warrantied, supported, stable, quiet and outstanding performers.
If you intend to use one in a semi or fully professional setting for Photoshop, Premiere Pro, Final Cut or other intensive Digital Content Creation task, they are hard to beat. Impossible to beat for legally running Final Cut or Logic Studio.
If you intend to use one for Internet browsing, word processing or checking email, they are a poor value for these and other less-demanding tasks.
They are also a poor value for running Windows-based games or for getting bragging rights to a high 3D Mark score.
Still liking my '06 quad for now,
Keri
PS. You will find no shortage of people that claim they can build a
FAR SUPERIOR system for half the price (or less).
No They Can't.
