I just backed up my iPhone, and it offered me iOS 8.0.2 (which I declined). Does that mean there have been two "fixes" since iOS8 was released, or is 8.0.2 the official "upgrade from 7" version?
8.0.2 is basically a roll-up patch consisting of 8.0.1 plus a new software updates (mostly) targeted at iPhone 6 users. Basically 8.0.2 replaces 8.0.1.
However I would still install on older iPhones if it is offered to you. There is no reason to decline it !
I "upgraded" to version 8 on my 5C. Ever since that was done I've been busy re-installing all my contacts. It somehow dumped the lot except five random ones, none of which are ones I've used recently.
How did you upgrade ? "Over the air" on the device or via iTunes.
Did my upgrade via iTunes and had no such problems with contacts, all my contacts were intact.