Ok so I can tell you a bit what you could need or just want, Ive got mine since a week after it has arrived in shops.
New Guide to x10 Users
JuiceDeffender - Must Have!
@info
JuiceDefender saves battery power (lots of it!) by controlling the mobile data connection, WiFi, Background data, Auto Sync and other battery-hungry components
Advance Task killer - Must Have!
@infoOne click to kill applications running background. This one is faster than free version. Features: click to select or unselect the app, long press to activate pop-up menu, Menu>Settings>Notification bar icon, AutoStart Ignore.
EStrongs Task Manager - Must Have!
@info
Save Battery,Free Memory,Kill
task,close everything,Uninstall app,Speed up phone
Swype - Must Have!
@info
Swype, the gesture-based typing tool that makes cellphone text input much, much faster.
Smart Monitor -Recommended!
@info
*App Task Manager:
(Clear Cache,Kill Process)
*CPU, Memory usage of System and single App
*Net Counter:WiFi, 3G, EDGE traffic & alert
*Battery Widgets
*Storage
*net status,IP
*WiFi ON/OFF, signal
*setting:Sound, Display, WiFi
Barcode Scanner
@info
Scan barcodes on CDs, books, and other products, then look up prices and reviews, or search for a word in a book and find where it occurs. You can also scan QR Codes containing URLs, contact info, calendar events, and more. Features: contact sharing, improved QR Code decoding, and added Chinese translation.
Meridian - Recommended!
@info
Meridian Player Android App is one of the best multimedia players for Android yet! Couples music player with video player, something not offered with the vanilla install on the T-Mobile G1 or Android phone. Meridian Player can playback the following formats: MP3, OGG, MP4, and 3GP.
@Solution for Battery performance
Keep you 3G off, don't need it don't use it!
Discharge your phone completely and charge fully and you will see when battery will lasted much longer.
Please rate and thank me if I helped you, I hope I did