I have my treo 750 now since a week. I do not sync it to my mac yet as I have to update it before. There are several small things which are more or less annoying.
One thing is that it is sometimes quite slow. The only third party app ist BB connect but the slowlyness issue already appeared before. It seems that switching between apps triggers it.

Number two is that the today screen is updated very slowly as well. For example if I read all new mails and go back to the today screen it will take several seconds till the display says no unread messages again. The small letter icon in the top bar will sometimes stay till I tip on it an cancel it away even if I already have read and deleted the mail that triggered the icon.

Another thing which was really making me unhappy was that when I received my first voicecall on it it was on the charging cable I plugged it out to be wireless and free in the room to my surprise I could not answer the phone anymore the screen was alright showing the answer possibility but the phone would not react :[

So far so good I will go on trying new things when I start to sync the phone.