Just a few thoughts for future features.
1) Add a layer preview stepping function where you can jump 1, 5, and 10 layers at a time. The scroll bar is very useful most of the time, but not very accurate when you have over 1000 layers and are trying to troubleshoot a print. Typing in the layer number each time gets tedious in very short order. :(
2) When at less than 75% fan speed on my reprap the layer cooling fan will not start. After I slice I need to go in and replace M106 S with M106 B1 S to bump the fan to full speed for 1 second so that it will run at lower speeds. I think that this would be a boon for people who do not have an Ulti, but still love Cura.
3) This comes from the engineer in me... I think that if the outer layer was offset by 1/2 layer height it would increase the strength of printed parts, help with delamination and give a smoother exterior. The down side might be in the loss of details.
Any who...just my 2 cents worth