The N900 can pull off 3.5G (HSPA+) on T-Mobil in the US, which is quite nice speed wise.

Not at all true. The first year I had my N900 I was on AT&T, limited to EDGE (2.5G), and was very happy with it. Now that I have a faster connection, I do use it a little more often, but I'm not using a ton of data, as most places I go I have access to wifi. When I don't I'm generally doing small things, like checking hours at a service location, or using a nav program that grabs it's routing info from a network source.

There are several users on here that don't even have a SIM in their device. They use skype over wifi for calling, or just prefer to have a nice pocket PDA with super-extended capabilities. The reasons for wanting an N900 are not limited to what you use it for, or even what it was marketed to do. While an N810 may be functionally able to do all these tasks, some may prefer the N900 form factor, or the active community around it (which you have to admit is a hair more active than the N810 community these days).

As to the OP: Yes. I would still consider a reasonably priced (<$200) N900 a viable purchase. They're still competitive, and very capable. If you want the latest whiz-bang (Angry Pigs), or IM protocol (wassapp), or the ease of use/setup of an iDroid, then it's probably not for you. If you want a kick-asp tinkering device, that can also be a stable phone and/or PDA, go for it.