I'm off on holiday to TAS hiking for couple of weeks and want to get a spare battery or two as I don't expect my single battery will last the 10 days at all. I'll be hiking in the wilderness and there will be no electricity to charge at all, so I need to get some spares.

So do I get OEM or cheap alternative?

Back in the days I had a 40D, I had an alternative manufacturer batter as well as the OEM unit. I really couldn't tell the difference between the two at all.

Any successes or ideas I should consider?

Looking at getting a 16gig CF card too, but that will be another post.