While I may be over stating it, to me there are two issues.
First the batteries that were linked are "drop in" so are not only likely to not live very long, and be at risk of actually having catastrophic failures. Now a setup like Mainsail shows is likely quite safe, but that is not what the OP was talking about doing(and seemed to be looking for support for the idea that it is a good idea).
Second, I see no advantage to the average cruising/day/live-abord/beer can racing sailor at all. Much higher cost, added complications, and potential dangers. Yes, lead acid can explode, or leak if mistreated, but it is far easier to contain acid in a properly designed battery compartment than flaming metals. The lighter weight, well it is weight low down so who really cares? is it worth ten times the price? Sure on a boat that is high end racing, OK but all normal, even on the hook needs, can easily be taken care of by standard batteries. It could be good for a very high end luxury yacht like Mainesail suggested, but for your average sailnutter, no way. I think you need a real reason to even think about using them. Heck how many threads do we see here about people who have ruined battery banks with standard technology, let alone adding in complications.
