Meh, Insanity in ME2 is more enjoyable/ challenging than in ME3. ME3 Insanity isn't really all that challenging, but I died more because the vanguard's Charge-Nova-Nova was seriously overpowered. Occasionally (and by that I mean only slightly less than often) Biotic charge will fuck up in ME3 and not allow you to use it when you should be able to, resulting in deaths that otherwise wouldn't happen.
Health is a lot more squishy feeling in ME3 than it is in 2. Also I missed the enemy health bars that were analogue-like rather than the blocks in ME3, they were much cooler.