I agree that IBM have done a lot to allow 3rd parties in, and also Microsoft have done a lot to simplify for us developers. Same there though, i'm not a Microsoft fan either. 🙂
Nevertheless, i also think that people developing for phones exaggerate how bad it is on phones. There are a lot of similarities between phones as well. Many use the same soc:s and probably also are based on the same development kits. Displays are also many times very similar although different brands, I think probably the baseband is the most difficult part, which is quite essential on a phone of course, but hopefully not all the drivers would have to be closed in one big blob the way it is now. I guess it's fair to say that this is all goes into kind of defacto standards, which makes it essentially different from the PC, but i do think it is possible benefit a lot by focusing on the similarities.