I like to think i stay up to date with current, useful technology, and it seems alot of people have google voice. So can someone explain to me why I should get it... why do I need it? why is it so useful?
Can't tell you why you should. The GV site is chock full of info and other sites such as Gizmodo have written guides on GV.
YMMV but for me, the tools for handling unwanted calls are a major point. I can have callers presented with a "number not in service message". I can choose to have them sent straight to voicemail and have the voicemail automatically deleted all without my knowledge.
The multiple phone ring feature is a plus for me as I work in a tower in downtown Houston and no carrier has perfect coverage in my building.
Call transfer is handy for end of the day teleconferences so I don't have to sit in my office for no reason.
The GV site is a big plus. I can read transcribed voicemails, listen to voicemail, forward voicemail via email, send and receive SMS with or without my phone (handy when I forget it), etc.
This probably won't apply to most but I found the virtualization of my number handy when switching carriers and not porting my number. I didn't want anyone to have the new carrier number as I wanted to force everyone to switch. Those calling my GV number never noticed that I had 2 devices on that number nor did they notice when I removed the old device. I can keep my GV number without having to deal with porting.
As I said, I can't tell you if you should get it. That's a call that you need to make for yourself. Really, you just need to look at the features and see if they suit you. It's no different than evaluating anything else. IMO it never hurts to try out something for yourself. You can test it out without switching everyone over to your GV number. If you find that you still don't see the point then don't use it. You can receive and make calls via your carrier number normally even if you do set up GV.
I like google voice and have had it since the invite days. it is great, however I will say that it can be surprising spotty for downloading VM messages after they are received and the app in general is pretty klunky. (No Delete off the Message Screen?)
I've had very little problems with the app.
As for deleting off the message list, you're overlooking the longpress (commonly overlooked in all of Android).