i have 3 of the newer 7870 tahiti le's. each overclock to ~1200mhz and mine at 500-520Mh/s
this is in windows running bitminter.

anyone thinking of getting a 7870, go for the sapphire one overclocks higher than the rest.
the xfx one is ok, runs slightly warmer than the sapphire (both have 2 fans)
the powercolor one is the worst fan usage is crazy fast/slow/fast/slow runs much hotter.