Honestly does it really have that great of an impact if your using a Tableless PhPBB or using tables in your layout? Which is more generally preferred and why.

The market today is pushing for the tableless concept of designs. If you are used to designs with table, it might take time to get accustomed to it but in order to be compliant or just be a part of the trend, I think it would be better if you use tableless.

If you know how to code with tables, you'll catch on to tableless XHTML fairly quickly. It's really just a matter of ditching table, tr and td tags for <div>.