L1 visas are terrible. You cannot change employers on an L1 Visa.
Years before you can change to H1B the next year in US, but lotteries made all these all changed.
They are better than H1 visas, because your spouse can work. Other benefits: no cap, faster path to green card.
Path to Green Card is long and arduous if its a L1B which is most likely going to be the case
Yes, although H1Bs aren't a great either. Most people I know who were on an L1 got their company to sponsor an H1 visa after a year or two and then change jobs a few years down the switch.