I know its very early to comment on the APP. I am sure the UI would be awesome and functionally the app is well tested..take care of the below things...(my english narration may not be that good, I am sure you go cool with that :) by getting the context)..Being a indian mobile testing guy, I can give you some inputs in testing point of view.
Perform an exclusive field test with major Indian cities and urban area's (very important). atleast 5 major operators in that area. / location (Airtel, Voda, RIL, Docomo, Aircel). Execute all the basic scenarios.
Power Consumption test:
Check the power consumed by your app, in foreground and back ground mode. use agilent 8960 spectrum analyzers / dummy batter / data acquisition unit, you can be able to achieve that. make sure you are not exceeding 100 mAh. (you can also try to find the power consumed by the competitor applications, such as whatsapp, nimbuzz, line, kakoo talk, wechat).
I am sure you have UX designers, but not presuming that having HMI certified usability testers. (Its hard to find in indian job market). but you can engage a company doing usability testing or you can hire some usability test managers, who can invite people (such as college students, various job backgrounds etc) to your premises and perform usability testing with them and get user feedback's... this is really important to get in to the users hearts.
Device compatibility tests:
app may be working really cool in samsung galaxy S3 or iPhone 5, u must be having one :). but may not be working at all in 3GS or a galaxy tab. It may just crash or some major functionality may not work at all. so create a comprehensive device lab with almost all the major devices. (you can also go OS vise, in android most of the people use 2.3 and 2.2 OS, if you just cover that you are 90% covered). you can also give a try with nokia RDA (very effective) or perfecto mobile's device cloud (bit expensive, i never tried due to that).
Standalone applications performance mostly depend upon the processor speed and the hardware make, but we can find out by benchmarking the performance constantly over a period of time. you guys might have done that already. but make sure you use android moneky or monkeyrunner (performance automation embedded tools from google). you can also try robotium to create a performance test suite (again this is for only android)
Dev team might have created good unit tests (now a days when creating project itself you will be asked by the SDK that you need to create a UNIT test suit for the product). Good unit testing will help the product to avoid most obvious defect leakages from the system.
Lab tests vs Field tests:
After many years of working in this industry, i found that in lab (office environment), you can catch hold of / or hunt down only 80% of defects. rest can be fetched only in the field or drive or from users...
In my experience, testing team can never be able to get all the defects which the users are getting. Its not becos they are not capable of doing so, Its becos of different environment conditions where the users are. (different networks, different processor speeds, different hardware, different usage patterns). so you must maintain an active list of people (can be fetched via your social media team). where they come into picture before every major release. they can provide feedback on the product, they can produce different feature requests (where the in-house product managers never even think of). giving some goodies or paying their mobiles bills etc will keep them active and they are real Gems :)
I am already receiving super awesome responses from your twitter account. create or maintain active facebook page (sorry if I a m not managed to see that, if its already there). Keep buzzing the social media with more news. more wishes. more moments. more contests. many people will be in. :)
And finally, you guys got a super young investor or CEO, I am sure this guy is gonna do wonders. Wish him good from Mr.R :)