Stick around with XHTML/CSS long enough and you'll hate IE so much it won't be funny.
The biggest issue is the box model bug above. There's some other nasty issues, but in general it's not very hard to get pages to work nicely among IE5+ Win versions. IE5 Mac has some of it's own unique issues, mostly with CSS 2 stuff. There is a 'box model hack' for Win-IE if you absolutely have to use padding and widths...it basically passes a fake width to IE (152px) then through a parsing error (hides the correct width from IE) passes the correct width to the behaved browsers. I prefer to stay hack free as much as possible, so I rarely use it.
TommyWillB, I started out programming HTML back on a C64 (300baud modem!)...old timer enough for ya? In the mid 90's I was still using a Unix Shell dial-in account, even though I had access for the new fangled SLIP/PPP method. Couldn't stand the new internet...was stuck in Lynx browsing, Pine for e-mails, and IRC via telnet. Amazing the change 10 years will bring about. 300baud vs. 3mbps ADSL <G>.
I gave up the tables for layout for numerous reasons. One of the biggest was due to the ease of updating and proper handling of the pages in the oldest of browsers and devices (PDAs, Cell Phones, etc.) which are becomming more popular. Also like being able to change the layout without having to touch the HTML code, or provide alternative layouts which don't require complete recodes.
The biggest reason is my distaste for hacks. Using tables for layout is the greatest hack of all time in web design. They were never meant for that purpose. It was a revolution, sure...but it's days have come. In 2 years or so you'll likely see very few professional designers still using tables in that manner. Those who do will probably be the unemployed ones. I have way too many bills for that to happen <G>.