From experience in converting table sites into exact copies but made with CSS only I regularly see savings of about 30% on code and in quite a few cases up to a massive 80% saving.
However, it does depend on the code used and a tightly written table site that only uses tables for the main structure can be comparable in size to a css version - although I have yet to see one that is actually smaller in size.
It also depends on how the CSS/html is constructed and I still see a lot of wasted divs being used even these days. Things like wrapping a ul in a div instead of using the ul as the wrapper. Wrapping heading text in divs instead of using heading tags and so on...
You already know the benefits of CSS as you have mentioned them quite clearly so I guess the problem is more one of application and how to make CSS work for you. The problem often arises in that going from tables to css designers often immediately try to copy table concepts and end up using hacks to achieve certain features that are specific to tables. The solution is to work with CSS rather than against it and use its strengths rather than its weaknesses.
If you are copying a well constructed table layout and you make the exact same thing in CSS then there may only be a small difference in code especially if you are not using nested tables and are already using some CSS. However, the CSS version will be instantly more adaptable, accessible and maintainable than the table version just by design.
Very few people actually use tables for layout these days especially now browsers from IE8+ are all supporting the table display properties anyway. For supporting older versions I'm not averse to throwing in the odd table element for an element that is too awkward to code otherwise but to be honest I can't remember the last time I used a table other than for tabular data and I probably code 3 or 4 new templates a week for clients.
There is a steep learning curve I'm afraid though and CSS does have many rules that need to be obeyed. (Remember how long it took you to understand tables (I'm still confused by them)). As you get more proficient you learn the correct methods to use and avoid most of the hacks needed.
In the end its your choice and boils down whether you want to keep up to date with what's going on and spend a little time learning some new concepts. Or you can just go back to what you know safe in the knowledge that it will work but not quite as well as it should :)