Do a soft reset of your phone. After the 2.1 update, your phone reboots, but for some reason an extra reset was needed to get speakerphone functionality back on my hero. Just in case you don't know, hold down both the "Menu" and "Phone" button with your left thumb and while doing that press the end call button on the right to soft reset.
If your issue is not solved after a soft reset, or if you are using a task manager, do not kill an app called "com.smithmicro.dm". this is essential for smooth operation of your hero. i had speaker phone issues too. i restarted the phone and added the following tasks in the ignore list of my task killer. Now hero running 2.1 update is awesome. you should add these in the ignore list of your task manager too. basically they need to be running all the time.
P.S. I am using Advanced Task Killer Free as my task manager.
I'm having the same issues plus others. I did a hard restart and the speaker worked fine. I had also been previously unable to get my BT to work with my home phone (it worked in 1.5). As soon as I tried agian to connect to the phone (maybe the hard reset had fixed both) it still didn't work, and now the speaker phone is back to not working.
Something is up with this update...