Welcome!
I've been using the 2200mAh battery I ordered with my Axim since I first got the unit. I keep the original battery around for a backup.
Yes, the larger battery does add weight and bulk to the unit, but if you use it all day long, then it will be worth your while to get the Extended Battery.
I am now used to the little "hump-back" that the larger battery adds to the Axim, and in fact, I use it to hold on to the device while watching video or reading an e-Book. The biggest drawback is the need for a case that fits the larger battery.
But try it with the original battery, and if you find you need more juice to make it through the day, try the Mugen batteries. I've read some good things about them here on Aximsite.
Keep Grinnin' Dude!

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The mAXIMum Dude 
Dell Axim X51v
WM v6.1
Dell Bluetooth GPS
Dell 2200 mAh Battery
Ridata 233x 8gb CF
A Data 4gb Class 6 SDHC
Sena Flip Case
iGo Stowaway BT Keyboard
Yafa Quad Point 4 Function stylus
Avery TripleClick 3 Fuction Stylus
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HP 320 LX HPC (Retired)
View My Axim________________________
I´m 47.92899% Geek (Super Geek)
An (X) denotes a Wi-Fi post from my Axim.
" I thought I understood the politics of the world, then I saw the world as a whole, not just fractured pieces, and all sense of nations and boundaries faded away.
I am an American, but more so, I am a Human, and I stand not for any country, but for all Humanity"