I've read that Lithium Ion batteries don't normally need conditioning - unless they've been stored empty for a long time. In which case they should be charged and drained several times to get optimal performance. In any case, i am relieved about that.
Being still on the fence, i did go back to t-mobile to look at the S5 one more time. It's a tough call... I really like that phone, but it doesn't feel any smaller in the hand really - it's so negligible. The screen does seem to pop out more... anyhow, I didn't trade in.
I think the solution for me will be a less bulky case. When I hold the G3 uncased in my hand, it's perfect. The bodyglove adds those square side bumpers all around which kills the nice feeling of the phone.
So I think I just need to find the awesome case and I am done.