Yep, MU is great, Fan-freakin'-tastic for reading older (and current'ish) Marvel titles. Not every single older issue is up on the site, yet, but they are getting there. Like it has been said, if you just want to read Marvel, MU can't be beat for value. It just can't
That said I do not enjoy MU's reader (its not terrible, I just wish it was better) and, also like said

, you have to keep paying each year (or month if you choose) to have access to all the titles.
Comixology has a better reader (I still prefer CrossGen's from back in the day) and once you pay for the title, you have it. Well, not physically of course

, but yeah, it is yours. And since Amazon bought them I think everyone's fear of "But what if they go out of business? What happens to my titles?" has been sated. So Comixology is the one to use if you want to "own" what you read and not have to worry about recurring payments. Plus, again, as said, they have some amazing deals and specials that come down the pipe from time to time (nothing like Marvel's recent Kindle sale, but what could beat that?)
Now if you are buying Image titles, and you should be checking into some of those *cough, cough Black Hammer cough*, they slide to a cheaper price, which is nice.
But Comixology's specials just kill my wallet. I mean, it hurts.

So if nothing else, buy a couple 99¢ comics and try it out (or just "buy" one of the many free titles they have there)
