Oh, I just installed it on a clean Snow Leopard and it's working fine - the driver listed is 3.18.02.0-00 (click About WWAN with Show WWAN status in menu bar selected on the network in System Preferences).
04/09/2009 21:09:58 kernel Warning - com.novatelwireless.driver.3GData declares no kernel dependencies; using com.apple.kernel.6.0.
04/09/2009 21:09:58 kernel Warning - com.apple.driver.InternalModemSupport declares no kernel dependencies; using com.apple.kernel.6.0.
04/09/2009 21:09:58 kernel AppleWWANSupport1: Version number - 2.0, Input buffers 16, Output buffers 4
04/09/2009 21:09:58 kernel AppleWWANSupport1: Version number - 2.0, Input buffers 4, Output buffers 2
04/09/2009 21:09:58 kernel AppleWWANSupport1: Version number - 2.0, Input buffers 4, Output buffers 2
04/09/2009 21:09:58 kernel AppleWWANSupport1: Version number - 2.0, Input buffers 4, Output buffers 2
04/09/2009 21:10:27 kernel IOHIDSystem::relativePointerEventGated: VBL too high (33529824), capping to 20000000
04/09/2009 21:13:43 configd[14] network configuration changed.
04/09/2009 21:13:43 configd[14] network configuration changed.
04/09/2009 21:13:43 pppd[191] pppd 2.4.2 (Apple version 412) started by [user removed], uid 501
04/09/2009 21:13:44 ccl[193] CCLWrite : AT\13
04/09/2009 21:13:44 ccl[193] CCLMatched : OK\13\10
04/09/2009 21:13:44 ccl[193] Initializing phone: ATE0V1&F&D2&C1S0=0
04/09/2009 21:13:44 ccl[193] CCLWrite : ATE0V1&F&D2&C1S0=0\13
04/09/2009 21:13:44 ccl[193] CCLMatched : OK\13\10
04/09/2009 21:13:44 ccl[193] Initializing PDP context: AT+CGDCONT=1,"IP","MOBILE.O2.CO.UK"
04/09/2009 21:13:44 ccl[193] CCLWrite : AT+CGDCONT=1,"IP","MOBILE.O2.CO.UK"\13
04/09/2009 21:13:44 ccl[193] CCLMatched : OK\13\10
04/09/2009 21:13:44 ccl[193] Initializing with secondary command: AT$NWPDN=0
04/09/2009 21:13:44 ccl[193] CCLWrite : AT$NWPDN=0\13
04/09/2009 21:13:44 ccl[193] CCLMatched : OK\13\10
04/09/2009 21:13:44 ccl[193] Dialing: ATD99**1#
04/09/2009 21:13:44 ccl[193] CCLWrite : ATD99**1#\13
04/09/2009 21:13:44 ccl[193] Waiting for connection
04/09/2009 21:13:44 ccl[193] CCLMatched : CONNECT
04/09/2009 21:13:44 ccl[193] Connection established
04/09/2009 21:13:46 configd[14] network configuration changed.
04/09/2009 21:13:47 ccl[193] CCLExit: 0
04/09/2009 21:13:47 pppd[191] Connect: ppp0 <--> /dev/**.wwan
04/09/2009 21:13:50 pppd[191] Could not determine remote IP address: defaulting to 10.64.64.64
04/09/2009 21:13:50 pppd[191] local IP address 10.122.239.153
04/09/2009 21:13:50 pppd[191] remote IP address 10.64.64.64
04/09/2009 21:13:50 pppd[191] primary DNS address 82.132.136.102
04/09/2009 21:13:50 pppd[191] secondary DNS address 82.132.136.103