i have both snapseed and photoforge 2 for my ipad.
if you want speedy editing i suggest using snapseed.
if you want an app with more powerful tools i say go for photoforge.
snapseed is fast and have an almost instantaneous response. i use it for smaller files and quick edits.
photoforge is more powerful, almost like photoshop touch. layers, masks, blending modes, the whole works with a few missing tools you can only find in photoshop touch. the only downside is that it has to render each setting change. blending modes dont appear until you click ok.
@bob there are photographers who edit their photos on the fly with their ipads. a lot of home users also use their ipads to send emails to family and friends. i use my ipad on location shoots to see actual results through photoforge (it can open raw files). its lighter than bringing a laptop and more portable.