I have spent some time evaluating the ESP8266 vs the EMW3165.
The ESP8266 has two fairly critical flaws; it does not have a sleep mode via the AT command set -and- just about every user of the part says it crashes fairly regularly and particularly with the AT command set. That (crashing) in itself is enough to make me take the part less than seriously. It is a 'toy' for those reasons and confined to applications where these attributes are non problematic.
I will readily admit that these two criteria may change in the future; a new AT release that solves both those issues may surface. For now (August 2015) they are real problems.
I have commercial need and those two problems in a person portable device are show-stoppers.
The ESP8266 however has a very good (comparatively) and reasonably active support forum. There are downloads of the SDK and documentation etc. Sure, it is a little difficult to find things like actual downloads at times, bit it is all there.
If I were going to spend time to focus on developing firmware for a WiFi device I think it would be for the ESP8266 for the above reason. Support.
I do not have the experience or time or inclination.
I can see the attraction of the ESP8266 for the Arduino users - and it is a great attraction. Until another product offers the same simplicity (AT command set) the ESP8266 will rein supreme and all the others will probably languish. The Arduino users are possibly ok with periodic crashes, can mitigate against it with power cycling techniques and maybe toggling RST low etc. Commercial users will possibly generate their own firmware for the device or bypass it or, like me, get one for play then determine where to go from there, probably not progress past the 'play' phase.
I like the EMW3165 far better and I wish it had the AT Command set and the reliability I've dwelled on (painfully probably) for the reason of its power consumption possibilities. However I have neither the skills nor the time to produce the firmware/software to use it. I need to focus on my application which is probably the same for 99,9% of the users out there.
I've looked through the posts on this forum and I can see some clever people here who clearly have both the skill and hopefully some of the time required to bring this part into a commercial success, assuming they are willing. I also see that the support from the manufacturer is somewhat less than the ESP8266 and perhaps this is as a result of time - it is a new part. I mean no disrespect, just that from my observations I see this.
The reason for writing all this is my hope than someone will go to the trouble of producing what I believe to be 'winning' firmware for the device and the manufacturer will actively support it.
You may accurately say I'm lazy and don't want to go to the trouble of generating my own firmware. That is true. It is also true that I could do it in the time available to me. I need to focus on my application - same as most others.
I would welcome feedback from developers/others who have used this device successfully.
I am a developer of person portable embedded systems with experience in mainly assembler for the MSP430 series processors as well as many older cpus, digital design and some minor Arduino experience,