Growing up as a kid, I was incredibly into comics (mostly 90s era X-Men titles and other Marvel titles). When I went to college, I kinda dropped the habit. Over the summer, after seeing the latest X-Men, I had a thirst for more comic goodness and ended up getting a Marvel Unlimited subcription.
Here are my thoughts:
1) Comics look GREAT on an iPad. The size/form-factor of an iPad (I have an iPad Air) is perfect for comics, and the display is awesome for the colors/pencils.
2) One time I tried to read comics in a web browser on my computer. This SUCKED. The general widescreen aspect ratio and the navigation felt weird.
3) The subscription is priced okay. It's not a steal and it's not expensive. You get access to a pretty huge backlog of Marvel titles. Most of the big titles like X-Men, Avengers, Spider-Man go back for decades; other more obscure titles are hit and miss but they are adding things over time. For current titles, you can get access to everything up to 6 months ago (e.g. you don't get access to the latest and greatest). This was fine for me, since I had so much to catch up on.
4) The Marvel Unlimited iOS app is OKAY. Viewing comics is a pretty great experience (see (1) above), but the app as a whole leaves a lot to be desired. For example, organizing what comics you want to read is really hard, it's difficult to piece together cross-overs, and you can't just "subscribe" to a particular title to get new issues when they get uploaded to the service. This is tolerable, but a little frustrating.
Overall, I'd recommend folks check it out if you enjoyed comics and don't absolutely need the paper copy/collectible anymore.