The integrated app crap:

txt only display is poor, not much graphic delineation in message list view or message view

deleting message, you must wait for it to delete on server before doing anything else with an un-dismissable dialog and when deleting a message over edge it can take a while

the retrieval and auto retrieval settings don't really work and get 'lost'

Your email gets intermingled with your sms and not in a good kind of contact centric way like some clients do now

I am sure there are some other things that led me to think it is crap, but I have not used it in quite a while