There is no software from HTC that syncs with Macs, according to their website. I haven't been able to do anything more than transfer files through the USB connection (but then, I was forced to inflict a Vista partition on my machine long ago, so I at least have some way to sync non-Google data, even if it's from my secondary OS).
For syncing music, check out doubletwist... for those of us who went from iPhone's seamless syncing to drag-and-drop, this program is a godsend. Don't know what to tell you about contacts/calendars/etc, though.
Check out this thread if you haven't already; there's some better advice there than I can offer (including a post by someone who suggests, but doesn't seem overly thrilled with, Mark/Space's Missing Sync... hadn't even thought of that).
I'm sure it's been pointed out in other parts of the forum but when you connect at first to your mac, nothing will happen.
-go to the phone, pull down the window shade, (the top black bar with the sync and usb icons)
-click on Ongoing-USB Connected'
-a pop up will come up with the options MOUNT-don't Mount. (click Mount..who wouldn't)
-Your Eris will show up as a unnamed drive!
You can drag and drop stuff directly to the drive or use Double Twist to add music, pics or movies. Double Twist tends to take a little longer, but converts movies to an acceptable format for your phone.
for the calender syncing. add your Google account to your iCal!
Meh... I didn't like Doubletwist. Perhaps the video formatting conversion is worth it, but moving music is still the same obnoxious drag-n-drop action, except it's actually easier to drag directly from iTunes into your SD card.
I just bought Salling Software - Salling Media Sync for Mac and it's exactly what I wanted. I've set it up to automatically sync my Eris to a specific iTunes playlist and a specific iPhoto playlist every time I mount the SD card. I created a smart photo album in iPhoto to include all photos from my 5 most recent photo albums, and I put all of those on my Eris.
If you're used to iPod's ease of use, this is the closest thing I've found.
Holy mackerel, do people not know that the ability to sync calendars and the address book with Google Calendar and Gmail contacts is built into iCal and Address Book on the Mac? Sync the Mac apps with Google and let your phone sync with Google directly.
There are also apps that do this a bit better (BusyCal and BusySync, plus Spanning Sync) on the Mac - they give you finer control.
Also, you can set iCal to sync with the CalDAV versions of your Google Calendars (which is what I now do.) I only connect my phone to my Mac when I need to copy a file over to it.