I think these need to be reduced a heck of a lot more than just 50%. With my whole URL + the G. Analytics tracking, all put into Mkto terms, the URL can be 6 lines long in the preview window. It drives my boss NUTS! A simple, mk.to/56ghe link is about as long as he wants to see it. Big Big Big plus! Though word on the street is the Q1 update will address this.
Pro * Prevents folks from removing my URL parameters and going direct to the LP, thereby losing tracking info * Looks pretty
Con * Not as easy for marketers to skim to make sure they're using the right link, might mix up links within a campaign, would rely on using URL shortener rather than just making a quick update in the email or other campaigns
In the meantime, you can always use the Google URL builder http://www.google.com/support/analytics/bin/answer.py?hl=en&answer=55578 to tag it with your campaign, medium, etc., and then use http://bit.ly/ to shorten that URL to paste into your emails. It's a few extra steps, but if you have a really long URL and want it to be pretty (like in text-version emails), that works fine.