It'll be incredibly slow compared to 9.2.2. :P
what exactly is slow in 10.2.2 for you? as mac os x - now and in the future - wants a decent graphics card for quartz extreme speed, your imac will be out of it for as long as there's mac os x. sure, 10.3 will be a bit faster here and there, maybe even much so. but what you perceive as slowness is a change in architecture that won't be 'solved' just like that.
you lost some interface speed.
you won a lot more. like real multitasking.
and all the other UNIX stuff...
Mac user since 1987. Running Mac OS X 10.8 Mountain Lion on a MacBook Air 11" & an iMac 27" and whatever's newest for my iPhone 4s, iPad 3 and AppleTV 2.
Apple Certified System Administrator 10.6, Apple Sales Professional 2008-2011, Apple Certified Mac Technician.