So, 1.19 means that page histories, instead of displaying the total size of a page in rounded brackets by each edit, display the number of bytes added or subtracted in the same way that Special:RecentChanges or Special:Watchlist do. This is on occasion useful, but there are a lot of things that, communally, we've built on the implicit assumption that an editor can easily see the total size of a page. An example, on enwiki, is http://en.wikipedia.org/wiki/Wikipedia:SIZERULE#A_rule_of_thumb - the general guideline rule of thumb for when a page has become Too Large, and should be split. It's based around size in kb, and the 1.19 change means that can't easily be found any more. Even on pages not ruled by this (talkpages, ferinstance) it's still a useful rule of thumb. The only real alternative is to wait until browsers start to lag before you do anything.
That being said, I find knowing how much was added/taken away to be really useful. Maybe it should be (pagesize) +bytesadded instead of having to choose between (pagesize) and (bytesadded).