Yeah, you get used to the extra space, but personally I prefer a site that looks the same for the majority of people. It sure makes it much easier when talking to clients to say "click the link on the left side" or saying "5th line down, it explains XXXX". Granted we use CSS on our text too and they can adjust the size of their text, but you get what I mean

800 x 600 good enough to preview your webpage.

I design with a min width of 800 but the web page is fluid so it doesn't look that bad on all resolutions

I recommend using 1000*600 for webpage because most people
use lcd with 1280 X 1024 display.

I go for flexible size when i comes to that.
but my base is 1024 X 768.

I would say 800x600. You never know who is still using this monitor resolution.

1024x anything has become standard now. 800xanythign is out now.