Quick primer on lithiums. This is based on some second hand knowledge, some personal experience, and some theory.
1) smaller and lighter, everyone knows this
2) CAN have more cranking power than lead acid but this is entirely dependent on the size of the battery (4,8,12,16 cells)
3) Total capacity for a given cranking amps rating is much less than a similar cranking amps rated lead acid. I'm told that lithiums can use a higher percentage of their capacity than lead acids but i've not verified this
4) lithiums require charging the same as a lead acid. If it gets low, it needs to be charged. The only difference is that a lithium battery will leak power at a much slower rate giving them a longer shelf life so they don't typically need to be charged over the winter
5) trickle charging is generally a bad idea for lithiums and most will come with a warning not to use a battery tender or similar trickle charger
6) They CAN be charged with standard chargers but generally speaking it's best to use a dedicated balance charger as supplied by the battery's manufacturer. There are some brands that have built in balancing circuitry in the battery but most do not. Chargers typically run around 50-100 bucks.
7) If a lithium battery is allowed to run completely dead it should NOT be recharged. Catastrophic failure does not always happen but it can. If it does it might not happen while the battery is on the charger, it might wait for a while before anything happens. Internal damage to the battery can lead to an internal short which results in massive heat buildup until the battery catches fire. I've personally lost a bike to this (I was riding it when it happened, thankfully it lost power before the fire started so I had already pulled over and gotten off before things got really hot). Lithium batteries are not inherently unsafe and despite my previous experience I continue to use them because I know the fire was my fault but it CAN happen if you're not careful
8) Lithiums do not like to be cold. On colder days they will frequently be unable to provide maximum cranking power. Usually, this can be dealt with in one of two way, either turn the bike on and let it sit for a minute with the lights/seat heater/other accessories on, or crank it once or twice expecting it to not fire up, then wait a couple seconds, then try again. Once current starts to flow in either case, the battery will warm a bit and provide more power but don't expect to jump on, fire up, and go if it's cold out. Unless you live in an area that's always cold or ride all year long this shouldn't be a major issue.
In general, if you can get by the expense, a lithium battery is a good investment. But like any other sort of "tuning" it requires a bit of extra care and maintenance over the stock setup. Failure to treat them properly can lead to major problems but treat them right and they will treat you right in return.