How do these websites work on the iPad? Twitter, Facebook, Tumblr. I know some of them have dedicated apps, but i'm wondering how well they work when accessed through the web.

They should be fine – although as you can get more than one browser for the iPad it will depend on which one you use as well…any flash parts on Facebook won’t work though.

Some websites will default to mobile version which I do find irritating in some circumstances. In these instances I use Dolphin HD (free I think) and set it to desktop mode.

It is a freebie - at least it is on Android - not tried it on my iPhone

How about Atomic web browser?

Not used that one in a while – I preferred Opera over Atomic but always found it quite good