An update to my findings:
Phone is a piece of crap sometimes at being....well...a phone. I try to make calls, nothing happens, get calls...can't hear the person. Have to power cycle the phone to fix it. GARBAGE. Anyone have a fix for this? Also a fix for how it takes forever to send a SMS message now?
Yeah, that's the "Silent Call Bug" that is also discussed in this thread.
http://forum.androidcentral.com/showthread.php?p=115355&posted=1#post115355
The only temporary fix for that is a reboot. Factory Wipes cure most of the other 2.1 blues but the that bug is pretty persistent.
It usually happens after somebody leaves you a VM and the minute you call to your VM to listen to it.
I've also seen it happen when someone calls you while your on another call, and they leave you a VM. Again, once you try to listen to it, it happens.
I've tried to reproduce these conditions but it seems to only happen when it wants. However it does appear to hover around Voicemail.
Here are a few other symptoms of 2.1 if you haven't seen them.
1. The "Silent call" or Phone goes Silent bug - This includes but is not limited to...
a: The phone not ringing when calls come in.
b: The phone lagging when using applications that require sounds for inputs such as the dialer app, volume control etc...
c: When placing a call, it will show you are connected but no sound will com from the earpiece, speaker, or bluetooth.
d: Phone will not go to sleep after setting it down.
[Solution - however temporary, a reboot will kick it back in shape.]
2. The camera resolution isn't as good - I personally have seen this, but I'm not so sure it's the camera itself. I went to my older photos what I had taken with 1.5 and they too look grainy.
[no solutions as of yet]
3. Weather app/widget force closes constantly - I have not experienced this problem but many have.
[solution - I've heard by going to manage applications and clearing the data for the weather app and widget fixes the problem.]
4. Contact ringtones stop working - this was due to still using a Task manager or task killer. The new "people" app that runs in the processes needs to remain running for all of your contact customization to work.
[solution - exclude the People app from the end task list then reboot your phone. Once you ended the people app process once it won't work right unless you reboot. Or remove your task killer and reboot.]
5. Battery life seems to be lower - I've seen this with my Eris, however if I refrain from playing with it most of the day the battery life is about the same as it was before.
[solution - I've seen this narrowed down to apps/widgets that use constant mobile network connectivity to stay updated. Also if you are using a battery widget, removing it will increase your battery life. Ironic hu.]
6. 50% or less signal - this is for everyone across the board. Haven't heard of any fixes however it doesn't seem to have a negative effect.
7. Calendar app force closes - Haven't had this one happen but it seems common.
[no solutions as of yet]
8. Text messages are really slow to send - After sending a text, it usually hangs. I've even had to delete and resend.
[solution - after factory reset, it was fixed.]
So far these are the most common issues I've seen myself and with other people's posts. I will suggest a factory reset once you've updated to 2.1. I had a ton of issues after the update but ALLOT of them were gone after I did the reset.