Ever since getting an iPod Touch I've been using Comicbooklover on it since that's the application I use on OS X as well.
The good thing about is that it's a free app unlike the full OS X one.
The bad thing about it is that it doesn't seem to get a lot of updates and that it's still in a somewhat BETA form.
So I tried an app called Comic Zeal, which I liked quite a bit for the most part, but still had a couple of rough parts as well.
Well, I somehow missed the latest update for it, which came out late November.
Since I had the night shift this past week and thus spent my breaks all by myself, I read up on several Super Play articles I wanted to read.
When I started up Comic Zeal 5, I noticed that everything was even snappier than before.
There's basically no loading when opening a magazine and flipping pages happens instantly.

The cataloging option is more robust and organizing sets is more straight forward than before.
Your personal zoom setting preferance can be saved by using the 2-finger zoom and keeping your fingers on the screen for a second or two, which makes it even easier to read columns of text spread along multiple pages.
In short, I'm really loving this app now after being "just" happy about it before.
The mini version is only for iPod/iPhone and costs €3, but the iPad version, which is also compatible with the iPod/iPhone costs €6, so I'd certainly recommend that one if you have an iPad as well or are looking to get the new iPad3 with the much nicer screen, which comes out in March.
http://itunes.apple.com/be/app/comic-zeal-comic-reader/id363990983?mt=8