I'm currently running a jailbroken iPhone 4 on iOS 4.3 GM. Cydia works and I currently have the following cydia apps installed with no issues:
Activator 1.5.4~beta2
Cyntact 1.4.1-1
Five Icon Dock 0.9.3202-1
iBlacklist 4.2-1
iFile 1.4.2-1
LibWeather 1.1.0.0
Lockinfo 3.0.1.0
Multifl0w 2.1.3
Popup Blocker 1.5.1.0
Recent/CallLog Delete 1.5.1
SBSettings 3.2.1
SpringFlash 1.3.1
TetherMe 2.0-59 (Personal Hotspot tethering works)
3G Unrestrictor 2.3.1-1
Also, pre-jailbroken IPSW's can be downloaded at:
http://jailbreakzone.com/2011/03/03/jailbreak-ios-4-3-gm-for-ipad-iphone-4-ipt4g-with-these-pre-jailbroken-ipsws-guide-from-start-to-finish-windows-and-mac/
To boot tethered, just write a batch file with tetheredboot.exe, iBSS, and kernel cache commands so the process is faster. Not really a pain at all (other than having to be tethered).