I prefer html tables over css becuase it works on 100% of the operating systems 100% of the time. Sure all you young wipper snappers have the latest and greatest browsers and operating systems. But that is not true for everyone, especially the average person over 40.
Remember just because it works on your computer it does not mean it works one everyones computer and people wont download software to view your page.
So as nice as CSS is, it can hurt you more than help you in the long run.
One issue you may have with the sliced tables is that dreamweaver is likely modifying the table tags and making them more CSS like than table like. Also, simple changes in the code like moving a tag to a new line can create spaces between images on browsers such as IE.
I use front page express which was standard on most computers before windows xp. I use it because it keeps the code intact and wont mess up the tables.
If you use an advanced program like dreamweaver, it assumes it knows more than you do and it makes changes in the code.
You can download front page express (that is express and not just frontpage) from microsoft for free and run it on XP I don't know about Vista. I don't have a link, but I have downloaed it before and have saved the executable. If you need it let me know and I can e-mail it to you.