i honestly dont know if it will or wont do anything to help decline microsofts monopoly. but i DO know that properly implemented, any AJAX app should be sufficently fast for most users. in fact, if people switch to vista like microsoft expects/wants then they will need a sufficently fast computer to do so. these people will probably end up having some form of broadband, so in this scenario, the users pc & internet connection are fast enough for most purposes. all you need then is a backend that's sufficently fast (mabye making use of some client-side things like spellcheck or whatever - just so you dont have to ask the server if every word is correct as an example) then AJAX apps should be fast enoug for the user to not be able to tell if office or weboffice is faster.
tho, i'm waiting for some cool ajax apps to come out, because i think it'd be neat to have a few apps running as a server on my laptop, such as a web-interface to share files (as samba dosnt work 100% of the time, and nobody i know uses NFS 'cept me). there are possibly other things but that's about it. hmm... rails comes with a webserver... mabye i should go make one...