I must say, I have had my battery mower, trimmer, blower for about a year now and could not be happier (Ryobi 40 volt stuff). The same battery works in everything. Just plug and play.
Yes, they are more expensive to purchase, probably 30% to 50% more than gas. But not having to buy gas, oil, mix it, pull on a cord a hundred times, change spark plugs, etc etc etc.
I do have a relatively small yard and I can mow it in about 15 minutes, then trim around the edges, then blow the grass away.
Yes, replacement batteries cost around $100. But I got one with the mower and one with the trimmer/blower. I actually only use one since it lasts for everything I need to do. So I have a new battery in the box that I can save until this one starts to die. Typical life is rated at 5-7 years.
In any case, just pressing a button to start things is so great. And don't think these things now are not powerful. I think the trimmer could cut your foot off if you got it in the way, not like the old electric stuff.
Rub a Dub