Hover a trimmed views field for full text?
Hate to answer my own bounty question but this works exactly as I want it.

I found a great way to do this with beautytips module. My field is an address (field_address). Add field_address to views and do rewrite->trim with ellipsis BUT exclude from display. Add the same field again this time rewriting the output of the field with:

&lt;div class="beautytips" title="[field_address_1]"&gt;[field_address]&lt;/div&gt;


(I have "Add beautytips js to every page" enabled in the beautytips settings)

+1 zhilevan's answer which is also a very good solution but is sadly missing the roll-back/rollup/close option which would mean very long tables with a few read mores open!