Transfer images to iPad from a second computer
Possible solutions:


iCloud sync.  I do this on several windows boxes using the iCloud control panel from Apple.  I am not sure how quality of RAW files are affected.
App store solutions may exist.  At the very least there are photo editors with Dropbox integration, although these have been manual processes for me in the past.
Koolertron 2 in 1 USB Camera Connection Kit+sd Card Reader for Ipad Ipad 2 
... An inexpensive alternative to Apple's photo connector


I find these things tedious, but it is better than it was when I first got an iPad.  I don't know that it is intentional on Apple's part, but more of a result of them owning the basketball ... How are you going to play ball without them? iTunes has been a pile of garbage for years, but it doesn't seem to hurt sales, so . . . . . . 

Good luck.

[edit] I have used PhotoForge 2, GoodReader, iFiles, and even email to move photos off and on to my iPad.  I like iCloud, as I can just sync back and forth from a folder on different PCs.  It took me a few tries to get it configured ... I also rely on DropBox, Box.net, and now Google Drive and Skydrive ... Many, many gigs of synced storage online.  Again, none of these necessarily meet your needs, your mileage may vary, and so on.