Pros - much lighter, longer run time, better performance (maintains voltage at higher level longer than all but the best NiMH race pacs),

Cons - more expensive than avg NiMH pacs, especially high quality cells, needs special charging protocol, CC/CV and a balancer to balance cell voltage. There may be more - these are the obvious ones that come to mind.

I started using lipo in 18th scale, best example I can give. Run time with GP 1100mah cells 9 to 12min. Run time with 1200mah lipo - 18 - 25min. Plus now, I can get a 1600mah lipo that will fit in the same space as the 6 cell pac used to go. I can also fit a 3S (11.1v) lipo if I want to do speed runs.

As far as esc is concerned - volts are volts. Where esc does matter is lipo needs a low voltage cutoff to avoid overdischarge which damages/destroys cells (depending how severe) and some escs have it (almost any brushless esc will have a lvc) where few brushed esc have it. This is getting better all the time - some of the newer escs let you run either brushed or brushless and have lvc. There are separate add on lvcs availabe too.