I got an Android tablet recently, so I've been exploring the various manga eBook options in a bit more depth. Before that, I did play with the various PC eBook apps, but now I can say for certain that the reading experience on a desktop or laptop is inferior to that on a tablet. Since I've dipped my toes into various eBook systems on both sides of the Pacific, I'm going to get up on my soapbox to say a little about each one.
But first, I'll talk about the general state of things. The biggest problem with eBooks for manga is image quality. Tone moire is a huge downer, and most of the stuff I've bought exhibits moire to some degree. Some are just plain bad scans though, and it's the lack of attention to detail that keeps me from enthusiastically going digital.
The second issue is DRM. The failure of JManga shows that the DRM zealots are absolutely right: you have little control over the content you've purchased. If the store goes belly-up or the licensing server goes down, you're SOL. So you have to ask yourself, is this store/service going to be around in five years? With the bigger players, there's less of a risk (you would hope), but some of the little guys might be questionable in that regard.
A few years ago I wouldn't have even considered eBooks, but after moving house a couple of times, I'm starting to come around. Books are light individually, but heavy in aggregate. And since manga tends to multiply like rabbits, it's a particularly painful situation. While I'm not really sure what I'm going to do in the long run, I'm exploring my options. This eBook tour is part of it.