Do you electrician-types think these have potential in a marine environment?http://www.blitzability.com.au/
Having a quick Google leads me to think that the jury is still out on this. There are a lot of promises and hopes but as yet no real world quantifiable data. It would seem that the end user costs are going to be on par with lead acid costs but offering twice the capacity. So I guess at the moment it is going to be "wait and see".
Only had a brief look at the web site and didn't see too much information on them.
1. You need to find out if they are suitable for short term high loads. Engine start or anchor winch.
2. How do you charge them, As in, can your existing charge system (240Vac Battery Charger, Alternator or solar) perform to there requirements or will need to be modified to do so.
3. What is their physical size compared to your existing setup. Will they fit in your existing battery space.
There could be more costs involved than just the price of the batteries. 
They're at a very early stage of development. Only one company makes them, and commercial production has only been achieved a few months ago. The technology does look promising, and because the raw materials are cheap and safe, there is scope for significant price reduction over time.
Operating voltage range is 30-59VDC. If you think that modifying a 12V system to work properly with Lithium batteries is a challenge (and it is), that's nothing compared to the headaches that retrofitting a set of these babies will bring with it.
Maximum current is a bit limiting too, in the current devices. The basic unit (S20) has nominal capacity of 51AH at nominal 48V. That's equivalent to about 200AH at 12V. This unit can only supply 15A, ie equivalent to 60A at 12V. So it's not going to run things like inverters or winches unless they're cheap and light enough to install 3 or 4.
