I have mixed thoughts.
My wife's Sertao has had the same lithium battery, the bikes stands for months and always starts immediately.
On the other hand I've been on trips where others lithium battery has caused problems that wouldn't arise with a conventional battery.
So for me they're not worth the weight saving.
Echo those thoughts, especially on the X Bikes where they are already very light and the battery is not very big.
I was photographing some specials for the magazines yesterday and the guy who builds them fits Lithium batteries so they can fit under the tiny seats etc - BUT, whilst they will spin a 750 triple happily, they don't work well with a standard rectifier, he buys in some special rectifier from the USA that adds extra resistance to prevent the battery from overcharging on the bike. The way he explained it to me was:
normal lead batteries have greater internal resistance, so any minor overcharging by the bike's generator can be 'absorbed' by the natural resistance. With the Lithium having much less internal resistance the battery cannot withstand any over charging, which is why they swell fairly frequently. In the last week, Foley motorcycles where I pop in for stuff and a coffee and the owner is a friend of mine, and an X Country owner (from new) - they have EIGHT bikes they have had to fetch this week alone, all with lithium battery problems. They were all blow up like a balloon and starting to melt too... the bikes rectifiers were simply not good enough to use with lithium batteries.
So, my take on it is:
If absolute weight saving, such as on a race bike where the last 1/10th mph is vital, then probably it is worth it and there is budget in the racing costings to fit a special regulator/rectifier.
On a special custom bike that has very limited bodywork and nowhere to fit a battery box for a coventional battery without spoiling the lines of the project... likewise.
However, on a gad about, shopping conveyance, jolly ride type machine - it simply isn't worth the bother and possible stranding.