Hi Andy
Not only will you miss the voice alerts but you will also miss out on the Mode S alerts, (i.e. non-ADSB Transponder alerts) and these make up quite a lot of the Commercial and GA traffic. Sorry if you already know all this but not obvious from your post.
For the extra cost of a Pi2B you will have the full functionality of the unit. If you choose to do this please do not redeem your bridge licence until you get the Pi2B as you only get one shot at the licence and it is tied to the Mac address of the Pi unit that you install it in.
I feel fairly certain that this will not be the end of the development of this fantastic unit and therefore you may find later that you are missing out on even more. You pays your money and you takes your chance.
Regards
Alan