yes, it will leave it with 4 GB less RAM. All work requiring RAM may now suffer more contention for RAM, affecting performance. Unless you can remove 2GB from each channel, it will also drop the computer into Single-channel memory, slowing it a bit more.
If you used integrated graphics that relied on RAM for memory, your machine will sink to its knees and beg for mercy.
Other than that, not ill effects. You may even save a little on electricity.