I usually have the last firmware, that is 1.6.6 now.
Do the app return the right temperatures? Can you paste here the livedata answer and eventual error report?
I assume that most people will have their firmware updated. so I'll rely on those user for a feedback.
A well design protocol should never break older versions.
This one specifically isn't very robust or future proof.
Since firmware check/support isn't a very common feature I would like to try to manage different firmware if possible.
That would make the app unique and useful (beyond the main scope of looking pretty, be straightforward and easy to use).
Another thing to manage is how different hardware can change how the protocol behave(one would thing shouldn't make any difference right?)
I use the GW1000 (GW1000B_V1.6.3) with an Ambient weather WS2902B as external sensor and I never had a single protocol problem so far.