For the most part, yes. At least, as far as 'Mechs go. Vees and Aero units changed too much with Total Warfare.
I think the only real change was in how Ferro-Fibrous armor was rounded. I think (and I could be entirely wrong), but any pre-TW 'Mech with FF should delete 1 armor point. (But it's not such a big deal with for a casual game.)