Importing: Export a vCard file from your other contact app (if you can), email it to yourself, open the email on the iPad, tap and hold on attachment, choose to add it to Contacts.
I saw a article the other day that said you should be able to drag a vCard file onto to the Calendar app in iCloud.com (with no address selected) and it would import. I tried this, but it was a fail. It looks like it will work, but does not, and the app goes all weird. Each time I tried to click on someting it opened a file dialog, only selecting the vCard file int he dialog did not work either. I had to refresh the page to get the app to work again. I was using the most up to date version of Safari on an iMac,. It should have worked with that setup if it was going to work at all.
I think this may work in the future, but has bugs now. Dragging the vCard file into mail added it as an attachment, so the basic tools are there.
Exporting:
I believe there are some apps you can get from the App Store that claim they will create and email and export file for your Contacts. That's all I know of. There is no option to export from either the iPad or iCloud at this time. At least nothing I could find. I'm rather disappointed. The MobileMe Calendar app could do both.