> Oil prices going down is a good thing for the economy.
That is no longer strictly correct. The ideal oil price for the US economy is a balance between high and low, which provides a high degree of employment for the US oil industry, oil production and export expansion remain high, and provides a reasonable price for US consumers when it comes to gasoline.
Oil in a range of perhaps $45 to $75, is ideal.
At $25-$35 you're going to eventually hammer the US oil industry and its jobs, as the hedges fall away. That will hit the US economy negatively at least as much as the low oil prices benefit consumers.
Russia is playing a bad game of chicken with Saudi Arabia and US oil, claiming they can endure ~$30 oil for a decade. It's false of course. Their personal incomes have been falling for six or seven years in a row. $30 oil will contract the Russian economy at worst, and stagnate it at best, so it would be ten more years of declining living standards in Russia (the last thing Putin wants to see, so it's a false bravado on his part, as typical).
Saudi Arabia and Iraq will be crushed fiscally by low oil prices. Saudi needs $83 oil to balance their budget. Canada will take a modest hit as well.
China is the prime beneficiary as a massive importer with modest production, they're in the position the US was in previously.