yes and no. First and foremost, even in its most raw 'optimized ' state the G5 is probably as fast or faster than opteron and co on x86 side. In terms of compiler support it is coming. Remember this time round with the G5, IBM are using the same processor with the same bells and whistles liike altivec etc.. in their blade servers, so they will be keen to leverage the power as well as is evidence with their release of XLC and XLF beta. What is also very interesting is that they are vigorously supporting the G5 on apples part, by specifically including flags in the compiler for optimizations for ppc970, blade , Apple G5 (all the same so far!) and support for older PPC with altivec! Also IBM have said in their developer network and Apple have also said that both companies are actively working with GCC to get its optimization levels much much higher with GCC.
IBM and APPLE will add autovectorisation much sooner than later IMO to GCC , XLC and XLF. Its in their interest as well to do this since they are now selling products with a 'G5' in it ... namely their blade servers.
As for leveraging the advanced cpu schedulers for extreme paralellism, that will happen over time. But again i would reckon much sooner than later, partly because i had no idea that they had such an advanced 'compatible' compiler like XLC and XLF available so soon after the G5 launch.
Another thing to note is that, why can't your apps start getting better optimized now!! XLC and XLF are avail for download now free from IBM website, since OS X is essentially another flavour of unix why not try recompiling some of your own fav apps your self.
As for manufacturers adding G5 optimizations, again i reckon everything is pointing to a healthy sooner than later. Apple are now providing XCode with their OS for FREE. XCode itself is evolving and is an evolving development platform, which means that developers have free access to it. It also means that unlike a developer using Visual Studio.NET, he or she does not have to pay huge fees for the latest and greates version which includes all the latest compiler tunings for the latest processor families. It also means that developers have instant access to the latest optimizing techniques that apple is providing for the G5 in XCode.
Not that i want to run down GCC, it does add some G5 optimizations. The level of optimization and speed gain you get depends on whether you simply do a recompile with GCC3.3 or spend a little time doing specific processor tuning with the provided tools and by writing specific code.
Obviously though the highest level of GCC optimizations will not at all be on the same level as XLC or XLF. But i mention this hear so you know that there is probably much more performance to be squeezed out of current GCC3.3 'G5 Optimized' code!
On the other hand currently optimized code built with GCC3.3 tends to be faster than the opteron running x86 optimized code. Check the barefeats results for that.
With regard to games, I think that there could be huge performance gains if developers bother to tune for G5, but how many apple users have a G5 just to play games?! Will developers tune for this small minority?? I think apple's biggest problem in terms of games boils down to a few things, none of which really have anything to do with the processor or system architecture per say.
1). Most Mac games are sloppy ports of PC games.
2) Most PC games use the Direct X API, which is not supported under OSX. its a closed API.
3) I believe that Apple have tuned their video drivers (particularly in 10.3.2) for 3d pro apps more than 3d games. I seam to get much much higher performance with this update in 3d apps like MAYA than i do in games! In the windows world a 9800 pro is great for games and not so great for MAYA, while the same card branded FIRE GL by ATI; but which uses 3d power applications specific drivers is crap at games but great at the power apps like MAYA and Lightwave etc...
That said it will be interesting to see what a company like ID does with its DOOM 3 on the Mac since they have traditionally been one of the few staunch supporters of the latest MAC technology and a powerhouse like the G5 would thrive on an app like that. Also its written in Open GL and ID (in myopinion) do not traditionally make sloppy mac ports. They put the effort that they deserve into their games.
Regardless though the pc will stay the games leader in performance and variety. This particular battle will never really be won unless Apple takes a more aggressive stance to getting games developed on and for the mac but working with development houses better.
Anyway, enough ranting! Night all, and in case i don't hear or see from any of you over the next few days. Happy Christmas, i hope its a great one for you all and Santa brings lots of powerbooks, powermacs.
Rgs
i_wolf
P.S. guys sorry for the length. Just its not a simple two line answer. I got flamed once for replying with a big rant like that, but remember it take more effort and a lot more time to write back a bit thing like that that just two lines!

so go easy!