I just recently sold my 3.0 stuff at Half-Price, and bought 3.5 replacements. I already had the DMG and PH for 3.5. I just used the extra change (got a small fraction of the original $$$ spent) to pick up the MM 3.5.
I did it because I prefer the spell fixes, and class fixes in 3.5 compared to 3.0. I also liked the integration of most of the meat from the original class books into the PH. I was actually surprised that there does not seem to be an MM2 3.5 (good thing I didn't sell that off).
I sold the 3.0 books:
PH 3.0
DMG 3.0
MM 3.0
all the class books (Tome & Blood, Fist & Fury, etc)
I now have:
PH 3.5
DMG 3.5
MM 3.5
MM2 (apparently still 3.0)
MM3 (already 3.5)
Complete Adventurer
I don't plan on buying the newer class or race books until I play a PC that uses them. Saves money.
I have not seen fit to buy the DMG2 or PH2, not sure what I'll really get out of it.
I did it because I prefer the spell fixes, and class fixes in 3.5 compared to 3.0. I also liked the integration of most of the meat from the original class books into the PH. I was actually surprised that there does not seem to be an MM2 3.5 (good thing I didn't sell that off).
I sold the 3.0 books:
PH 3.0
DMG 3.0
MM 3.0
all the class books (Tome & Blood, Fist & Fury, etc)
I now have:
PH 3.5
DMG 3.5
MM 3.5
MM2 (apparently still 3.0)
MM3 (already 3.5)
Complete Adventurer
I don't plan on buying the newer class or race books until I play a PC that uses them. Saves money.
I have not seen fit to buy the DMG2 or PH2, not sure what I'll really get out of it.