Since you're asking... I'd say no. Especially since there is no direct comment from Nokia about its upgrade path to the forthcoming MeeGo OS. Sure, the N900 will be the ARM platform for that OS, but that (historically) does not mean that it will receive the upgrade.

No sense in buying a phone without a clear update path and with a learning curve that ultimately might doubly make it not worth it if I were in your place.

So no. Don't buy.