If I switched, then:

• No more phone hopping; from Nexus One to iPhone to Palm Pre etc.
• Having the possibilities of having Bing as my default search engine; this can easily be changed I hope.
• Have to pay the pesky termination fee to AT&T.
• No Nexus One or Nexus S.
• Losing the unlimited data plan.

The good news is:

• Verizon has a better network than AT&T; so Verizon says.

Most likely I’d stay with AT&T just because I can do the phone-hopping without having to call Verizon. That’s the power of SIM-card. Even if Verizon were to support some kind of SIM-card, I wouldn’t be able to use the Nexus one as a phone anymore. The Wi-Fi Hot-Spot feature is a killer feature for me, especially without having the tethering plan.