I'm a fan, for a few reasons. DS1 lost a lot of weight due to my crap boobs and four days after his birth we were back in hospital. I was to give the boob first at every feed and then top up with formula from a bottle while I was pumping. I also had to wake him up to feed every two hours, no matter how long the previous feed had lasted, but that's besides the point. Don't do that. It's hell.
Anyway... when we got home a few days later my boobs were in a better state, having been kicked into action. At that point I breastfed and pumped round the clock, except for about 8pm-midnight, when I would hand him over to my husband. He'd give him the tiny amount of breastmilk I'd managed to pump, then use formula until I'd had a decent lump of sleep. There was no nipple confusion, no issue at all, but I was constantly warned that he might prefer the fast-flowing effortless bottle to my boobs, hence why we didn't do any more than that.
At five weeks or so we cut out bottles altogether, as I still couldn't pump anything near a full feed and he seemed to be having problems with dairy (it either cleared up or wasn't that at all).
Short version: combination feeding is a life-saver, a sanity-saver and gives someone else the chance to bond during feeding, but it probably best used sparingly and tactically so that you can get sleep. And pump! Lots!