If you are on the go, chances are you can't sit down and program for 2 hours straight. If you don't have that time to write code, you are better off describing your idea in pseudo code or flow chart and then find time to sit down and do the real coding. If I want to work on my codes, I need 1-2 hours of uninterrupted time at least. If I don't, I work on documentation, forum, and blogging 
BTW, if you really want arduino IDE on the go, don't buy an expensive toy like an ipad, but a real computer in tablet form factor. There are plenty of win 7 tablets around the ipad price. You can install anything that runs on windows, including arduino IDE. I'm trying to get one or wait till the second or third quarter this year for a win 8 tablet.
I am thinking about these two tablets:
Both dual core processors and the expensive one has 4GB ram. ipad2 only has 512MB ram and it keeps dumping webpages to free ram. I'm not even running many apps. I keep closing them to free space but still 512 is way under equipped for a $600+ toy.