Something to think about in regards to clock speeds and prices
Something we should really take into consideration is that a dual G5 2.5 GHZ processor (if it ships in July) will be the highest clock speed for a mainstream 64 Bit processor. AMD ( the only real comparison) with their Opteron CPU has only just shipped a 2.4GHz part and this part is in very limited availability.
Also if we look at pricing to build similar units, (and I mean actually using decent parts in the PC/Opteron and not just the cheapest junk you can find) you will notice there actually isn't much of a price difference at all.
Here is an example of parts available in Toronto, Canada for a good Opteron build:
Remember these prices are in good old Canadian dollars and the exchange rate is about $1.35 CAD for every $US dollar.
Opteron Box
2 2.0 GHZ CPU $689x2 $1378
MSI*K8T Master2 FAR K8T800, Dual CPU $315
KingMax 256MB*PC-3200 DDR400*SDRAM $73 x2 $146
Lian-Li PC-68 Aluminum Case $198
Antec True 430 PSU $109
Pioneer DVR-107 OEM $127
Seagate 160 S-ATA 8MB Cache $168
Sapphire Radeon 9600XT 128MB*DDR $244
Win XP*Pro Full OEM *for sale with system only $229
Microsoft Keyboard PS/2 & USB*OEM $39
Microsoft WheelMouse Optical OEM $23
BT 3-port FireWire 800 PCI*Card $68
Opteron 2.4GHZ option $1139x2 $2278
Dual Opteron 2.0 GHZ System $3044 Dual Opteron 2.4 GHZ System $3944
Notes on the above systems, the Li-an Li Case is nice but nowhere near as well-built (or classy looking) as the G5 case, and the included G5 keyboard/mouse are nicer as well. If you want to go with liquid cooling in your 2.4GHZ machine the cheapest full kit I could find was:
Thermaltake A1604 Aquarius II $174.98
Could you build the same system cheaper? Yes, if you want to use inferior parts that don't compare to their Apple equivalents.
Now the equivalent Apple Systems are as follows (modem removed since their is no modem in the Opteron System):
Dual 2.0GHZ Apple G5 Upgrading to 9600XT and removing 56k modem = $3528
Dual 2.5 GHZ Apple G5 removing the 56K Modem =$4158
So our price difference for very comparable systems is $484 for the 2.0 GHZ systems and $214 for the 2.4/2.5GHZ systems (only $40 if you go with the liquid cooling option).
Of course there are cons for each system, like no PCI-X or independent PCI buses on the Opteron systems (the lack of independent buses is vital for AVID DNA users, and other high end external storage usages), lack of room for drive upgrades on the G5 systems, and lack of higher end video card options. Of course when you purchase the G5 you get to use OSX and have access to Apple's wonderful pro applications like Final Cut Pro, DVD Studio Pro, and Logic Audio.
All I'm trying to say with this rambling post is that the current G5 lineup is actually a pretty good value for the power that you are getting. I'm not a Mac Fanatic per say, I've got three computers in my video lab 2 PCS, and a Powerbook, but I do feel for top end pro stations these new G5 towers are great products. Of course if I have the money I'll buy both an Opteron system and a G5 2.5 GHz but that is another story.
take care