Happy to read someone else out there w/ a 1.6 PMG5. I love mine, it runs Adobe and Macromedia apps great and powers my 17" studio just fine. Not to mention, no real issues with Tiger on this either.
I too have the same specs with RAM, HD. The graphics cards seems suffice and I am a designer, but let me know when you upgrade or find a decent card boost...!
Cheers.