My only experience with the airport extreme is from last Thursday evening when a coworker contacted me at home as her VPN wasn't working. After working on it for 30 minutes and noticing some odd behavior (Phase 1 negotiation worked fine, but Phase 2 was a no-show) I finally asked if she happened to get a new router as it was working fine for her a week or 2 ago. Her reply "Yeah, but why should that matter? It's just a wifi router. And this is a $200 Apple router, must be better than a $50 linksys."
😡😡😡😡😡😡😡
Little did I know the airport extreme has no web or ssh access. Everything must be done though a built-in utility in OS X, or a downloadable utility via Windows. I'll just say this utility leaves much to be desired and leave it at that.
VPN passthrough is advertised as a feature on these, but doesn't work, at least not with the latest firmware and perhaps certain combinations of VPN clients and hardware.
I told her to get a "real" router, even one of those refurb e3000's for $45, but she likes the white Apple one. 🙄
On the other hand, the e2000's & e3000's I've worked with have been great, both work excellent with stock firmware and support dd-wrt and tomato if you desire. I haven't heard anything bad about the 4200's though I don't know the status of alternate firmware availability.