Thank you guys for your prompt input. I'd say it's 80% gear lust - always want something more expensive, aren't we all?! the other 20% would be cleaner picture at high ISO. I saw amazing pictures Teamspeed presented in his 7D high ISO mini-review. but whatever I tried, I couldn't get that clean look in my shots. I don't know if it's just copy variation or my poor technique.
I do believe full frame sensor is better than a smaller one - it doesn't take an expert to understand that. I mean, simply look at the price difference between 7D and 5D mkII, whereas general consensus is 7D is a better camera than 5DmkII in every respect except the sensor.
Another thought is I'm an average hobbyist who seldom shoots sports etc. which the 7D is good at. When I went from 450D to 7D, I did find AF became easier and more reliable. It's always good to have more AF points to choose from, makes me more comfortable when composing. But looking back, I can't recall I had any problem with the AF system of 450D. so I think it's good enough at least for me.
I have trips scheduled for the coming holidays. I will try borrow a 5D mkII body from a friend to get some first-hand experience. don't know if it's available. Anyway, I'll think about it.
Finally, I have no intention whatsoever to argue the merits of the two bodies. It's just some lonely guy thinking out loud
Thanks again for your input - I might as well say "helpful", but again it will mean a hole in my pocket 
