It is worth remembering most of the GPS advocates posting here (of which I am one) are flying behind a panel mounted RNAV approved (and in many cases approach approved) moving map GPS, or are using a quite slick aviation GPS. Additionally, of the ones I know personally, I believe all of them have subscriptions for updated data on every ARINC cycle.
From this perspective it is almost inconceivable that you would want to use something else as your primary method of navigating under IFR (unless you have a DME/DME FMS as well
).
I have never found the DIY solutions sufficiently robust to be comfortable using them for anything more than additional data. Yes I do have a bluetooth GPS I can chuck on the dash and feed data to my tablet running other mapping products. Would I choose to use this as my primary nav system? No.