The next best bit is scaleability. I can scale any object as large or as small as I like. It's one of my pet hates in the IRL scrapbooking that flowers are often a certain size and rarely teeny weeny, so usually the size of the flowers you have determines the scale on the page. Of course, with any flat embellishment you can scan it into your computer, scale it up, and re-print it, but this is time consuming.
And I love the ability to shift things around, change things at the last minute, or scale everything just a bit smaller or larger to get exactly what I was looking for. Can't do that once the IRL page is stuck down (well, I can, but I have to be really creative and if anyone could see it IRL they would see I've made some kind of error there and tried to cover it up! I can even come back into a page and make drastic changes - like change the whole page from blues to oranges!
Competition palettes are also easy to match. I simply put the palette in as a layer and then select the colours off it, or move my object next to the palette colour it is to match until I have just the right shade!
I also enjoy working with layers, though perhaps this is more so because I've scrapped IRL for so long. Technically its all about layers - what is on top, and what is underneath, and the mix inbetween.
Sometimes layouts are heavily complicated in the layers - I can have 100 or so layers in play. Other times, there may be only 30 or less layers. Time is a factor, but really its what I want to produce on the page and how intricate I want it to look. I have attached some of my digi pages and how many layers were in play to create them. For each drop shadow is a separate layer (in most applications) and that adds to the complexity.
The number of layers means more brain management to make sure no one layer disappears from view or interacts in a way that I don't want it to. It doesn't necessarily mean that I've spent more time on that layout. I can spend just as much time getting the effect I want in the filters or overall look to the page and layout. Just like scrapping IRL sometimes its a breeze and everything runs smoothly, other times its hell to get the page to where I want it.
I also like how I can export out from the original file any size (mb) I want and this file will be the one I upload online. My original workings file stays in place until I decide to delete it.
There are lots of programs out there where you just pop your photo into a hole and the smashing page looks amazing around it. I'm a purist - I don't use any of these. Every page I make up from scratch using items from digi kits or my own photographs. Having pre-made templates is good if you've got lots of photos from one event (like a wedding) and just want to put them in and get something printed out, but I enjoy working from scratch and having full control over the layout.
There are some things I don't like about digi scrapping, but the points above probably mean that I won't give it away any time soon.