I could see it if you're committing to a cordless outdoor tool line, maybe. On its own... $300 for a junk saw (it would be a POS if it had an engine) and a spare battery (which I'm sure you'll need to do much work) is $180? You're nuckin' futs... you can nearly buy a Stihl 261 with that money, and what it costs in gas & any repairs, the cordless would cost you double in replacing batteries.
I guess it works if you have a small lot, and could buy the matching trimmer, blower, edger, whatever, and only need 1 or 2 batteries because you're not using anything for long. I take care of my gas tools and they fire up just fine when I need them, I'd rather spend more now and not be buying a $150-200 battery (or chucking it for a new tool) at 4 or 5 years with relatively little use.