How do you connect to your mail server? I use IMAP and the deletes propagate just fine. Most of the complaints I've seen come from BB owners where the default behavior is often to leave the messages on the server when you delete them from the BB database (the Droid obviously doesn't know which messages you've deleted on your local BB so it downloads them all).
BTW, not really a "Motoblur" issue - that's just a default UI. The underlying mail handlers are the same and you can always get another mail reader if you want.
Personally if you're not unhappy with your Droid there's no harm in waiting. I jumped ship from my Storm for a better browser, but unless there's something special you need from the X that the original can't do I can guarantee that the longer you wait the "more specialer" phones will be. On the other hand, if you're on an annual upgrade path my guess is that a decent selection of LTE-enabled smartphones are about a year away which is why the timing was perfect.