Examples include cortex-a57 vs a53. Alpha 21264 vs alpha 21164. As well as many of the atoms until very recently vs core2 and similar chips.
With the various arm derivatives from qualcomm, samsung, and apple a under 2 GHz in order CPU doesn't sound particularly impressive. Especially when they talk about "under 30 watts", that's intel territory, not tablets let alone smart phones.
Trying to emulate arm and beat arm on price/perf or perf/watt seems like a long shot with an in-order mips64. Similarly beating intel at price/perf or perf/watt seems exceedingly unlikely with lower IPC and a MUCH slower clock.
The only thing that makes these mips64 look good is the even slower previous generation mips.