I never really felt the iPad was suited for that kind of work - At least, I only ended up using mine for todo list, presentation note taking and PDF reading. Everything was just so much more efficient on a computer. And that's my research experience over the last 5 years.
If you had your iPad with you everywhere, it may be useful as a lab book, but in my experience, it wasn't really suited for it either, since you always end up with data that is either cumbersome to input, or doesn't render correctly using whatever apps you have, or is just plain awful to manipulate using the same apps.
PDFs and notes, awesome. Everything else, forget it.
Edit: I used Evernote and Papers. And I am really trying for an alternative to Papers, but so far the only alternative is Readcube, but they are waaaaay behind in features. Fortunately, they at least have a developer team that seems to respond to user requests.