Ummmd and Ahhhhd for a long time over petrol vs cordless and ended up getting an 18V Li Ion Bosch cordless hedge trimmer.
So far I love it.
I have borrowed a friends petrol model - mostly for trimming over Murraya hedges. It obviously doesn't have quite the kick that a petrol model has but it is very light, there is little noise and no fumes. When you hit something a little thick, instead of jamming it auto reverses until it nibbles through. It is noticeable but goes through quite quickly.
The battery is the same as the cordless drill range so if you had a bosch 18V drill it would be a nice extra.

Been skulking around on the forum and finally have something to put in my 2 cents worth. Had also got the Bosch Cordless Hedge Trimmer after considering getting a petrol unit.
Have used it over the last 2 months (about 10-12 times)
Adv:
Quiet, easy to use/start/stop
No maintainence/fumes
Powerful enough for most hedges
Similar battery to other Bosch units

Disadvantage:
Had pressed as fulfils my needs

Like the sound of the battery powered option. I'm still a bit worried about the battery life and getting stuck half way with a half cut hedge. How long does a charge last?

I haven't managed to run it out yet. I don't have kms of hedge but the LiIon are pretty impressive - it is the same battery as the standard 18v cordless drill. If you wanted multiple batteries it would probably be cheaper to pick up a drill as well.

I have one also. I think I get about 30 mins, not sure tho. But the battery really doesn't take long to charge, and if ur concerned then a matching Bosch drill will help you out nicely

This is my first hedge trimmer, but I've borrowed a friends corded one which I found to be cumbersome and difficult. The Bosch is great: light, powerful, lithium battery...all good

When Adam was a boy I bought a cordless ozito hedge trimmer for a friend as it was light, cheap and easy for her to use. I modified it slightly and it has performed flawlessly without sharpening or maintenance until now, the NiCad batteries won't hold charge. Their replacement cost is as much as a new unit and the repacking cost much more. It doesn't make sense.

After I used this tool for the first time I gave it a full recharge and put it away. Nearly 6 months later I have pulled it out and have done 30 - 45 mins of on / off trimming without any further charging - still in disbelief.
I had heard that Li Ion prefer to be left fully charged and have a very low amount of standing loss, but this was beyond any expectation.
Sorry to drag up an old thread but thought it was definitely worth a mention.