We use Marvel Unlimited because there’s not a great alternative for our specific purposes; but I, at least, am pretty reluctant to recommend it.
My biggest problem with Marvel Unlimited is that its interface is godawful unless you’re reading on either a tablet or a monitor at least as tall as a comics page (actually, the interface is still awful then, but the lack of a usable zoom function matters less). Yes, there’s a panel view, but it’s nigh unusable—it’s choppy, it frequently entirely omits parts of panels or entire panels, and it’ll throw panels and even pages out of order. I read on an 11″ laptop, and it sucks, hard. I can’t even imagine trying to navigate that mess on a phone.
It’s also worth noting that the Unlimited library is big, but it isn’t comprehensive; and the gaps often fall mid-series. For instance: If you’re thinking of subscribing mostly to finish up New Mutants, you are going to be sorely disappointed.
With the above in mind, I would recommend looking through the Unlimited library—seeing what’s available and what isn’t—and maybe waiting until Marvel has a free or discounted trial-period offer (which happens pretty regularly) to test it out and see if it’s what you’re looking for. There’s also the new scribd library, about which I know literally nothing, but which sounds like it might be worth checking out.
There is another alternative, one I’ve recommended before and will again for anyone working on a more flexible schedule than ours (basically, anyone not doing high-volume research for a weekly podcast): your local library. If they don’t have the books you’re looking for, talk to a librarian or check the computer system to see if you can request them via interlibrary loan. Comics collections are becoming a more and more standard part of library collections, and if you’re not wed to digital, they are a fantastic resource that far too few people take advantage of.
Best of luck!
/Rachel
Wholeheartedly agreeing with everything Rachel says above, but especially the part about hitting up your local library (and using interlibrary loans) as a way of catching up on the comics you want to read. I’m spoiled being where I am, because the Multnomah County Library system is amazingly good, but nevertheless: libraries, people. They’re your best friend when it comes to that whole reading thing.