I was simply pointing out that KGT+'s side button setting basically overrides whatever has been assigned to the built-in side button setting.
Actually, it doesn't override the key, but you have to be aware of how it works:
In "hold" mode, KGT+ hesitates a moment before acting on the key. So if you press and release quickly, the key performs its normal action. This is how ClockPop5 works (only on the regular hardkeys).
In "press" mode, KGT+ acts immediately but then watches how you choose to dismiss it. If you press the same key again, it dismisses, then sends that key, so you get the key's action on the tail-end. If you touch the screen or press a different key, it simply dismisses, so you don't get the key. "Press" mode is a special mode that ClockPop5 does not do. I like it because it leaves the display up, basically forever if you like. It refreshes periodically, too.
*BUT* it turns out there is a bug in the latest beta on "press" mode

. It dismisses okay if you touch a different key, but if you touch the same key twice it won't dismiss. So, don't try that just yet!
As mentioned, the side button is "special" on the 650 - it doesn't power the Treo up. Also, it's really kind of a sucky button - on mine it's very stiff and gives almost no tactile feedback. So it's hard to be very precise with it. The other hard buttons are great. The advantage of it however is that it has very few other functions so it's easily used for this.
My favorite key at the moment for mapping KGT+ is "while holding ... Center". With the way press/hold actions are implemented in KGT+, the only thing given up is the ability to do a Center-hold to get to the attention manager. I might be able to special-case that.