I've just bought a Buffalo WBR-G54 and a couple Buffalo WLI-CB-G54 CardBus cards. I've got it in 802.11g mode only though as I'm migrating everything over to 802.11g from 802.11b.

The speed seems fine to me. I can get about 20mbps throughput but that's with no 802.11b equipment. If I turn back on 802.11b support in the AP and have it start to transmit then the entire network drops to around 6mbps.

Security is in theory pretty good. When you upgrade to the latest firmware for the AP it gives you WPA support. I've enabled WPA-PSK (PreShared Key) and AES encryption. It's much more secure than WEP and RC4 but isn't backwards compatible with older equipment. You'll need upgrade the firmware on older equipment to support WPA. Most older equipment also doesn't support AES so you'll have to do a hardware upgrade for that. You can use TKIP which is hardware compatible with old hardware though.

Range is about the same as 802.11b but the speed is improved at lower signal strengths.