I will probably get flamed for posting this, just because people are so fiercely divided on issues like extended batteries.
I'm going to put my opinion out there for anyone on the fence though...it might help.
I ordered with my corporate discount...ever since the extended battery showed up, I knew I had to have one. I was pleasantly surprised that the ordering system let me add one to my basket when I got my phone. For $35 bucks, this thing could be pure crap, and I probably wouldn't shed a tear.
Sure enough, there it was when my overnight package showed up. I never even bothered with the original battery or battery door. Popped it in, plugged it up...yeah, the charge time seemed excessive, but beyond that, there I was with my brand new phone.
Now I live in Dallas, so I immediately went to the actual speedtest website in the browser and rocked some 4G...it seems like there is going to be some nice utility there.
Then I got in my car and drove to Austin for SXSW...and here I am at work on Monday, and I'm at 27%...haven't charged once.
The moral of the story, in case you aren't aware, is that Austin is not an LTE market.
I can't speak for 4G, because no one can. You and I are both early adopters. This may be the price we pay for being in the front row. Did you really expect sunshine and roses? I'm guessing these devices won't see acceptable thresholds of juice until we are running custom firmware...guys...that's why you got the HTC in the first place and not the Atrix...
That's why Verizon is forking over unlimited 4G when they admitted that tiered plans will be here as early as May...that's the price of admission.
So let me make a recommendation that I don't consider bold at all.
If you are in a 3G market and have problems with the battery life, cast aside a little vanity and double your battery life...the extended battery will probably be one of the best price/performance ratio purchases you make this year.
If you are in a 4G market and are unwilling to sacrifice an extra quarter centimeter of depth on your phone to double your battery life on a device that was rumored to have suboptimal battery life long before it launched...
Ain't that 14 day return window grand!
Seriously, does the extended battery door REALLY make a difference to you?
If you answered yes, good news...I heard Verizon just got last year's iPhone 4 in, and it's a very slim device.
EDIT:
Would like a case that fits (my only gripe), but that's how the cookie crumbles.