alt131 - 7:41 am on Feb 21, 2012 (gmt 0)
As a quick response, you are right about being uncomfortable having to add extra code - and being concerned about nesting. The other side is that if working with existing themes that may be your only option without re-writing the theme itself, and browser engines (well at least firefox) are now written so id's are stored in a hash which means they are actually fast and easy to access. (Note you should really only need to id the specific element you are targetting to increase the weight.)
Another option could be to take advantage of more advanced Level 3 Selectors [w3.org] (go to section 2 for a list).
... and to the "lurking" css-er currently working with wordpress a lot" Your experience is invaluable here. Can you make some comments about how you deal with this sort of issue?