I usually get digital comics on weeks I can't go to my LCS or shipping would costs too much. For me there are really only two down sides to this: Not supporting comic shops and how incontinent it can be when you want to read a issue but can't. Either because of lack of internet access or privacy to enjoy the comics.
For DC their books go down in cost after awhile but Marvels' don't. At least I haven't seen this for their current titles. While I do enjoy having a physical copy it's nice to know that I'll be able to reduce space and if I like the title enough I can get the trade later on. I'm also a fan of the guided viewing option that takes you through the comic panel by panel. I just really like the convenience but I'm not sure if I'll convert completely.