I almost forgot to mention about the new writer too lol taking a print screen of it now. Both have a totally difference interface and as for function I am not sure, maybe they are still the same or maybe more stable? No idea at the moment but most of my friends were complaining about the new messenger.
As for me I got no complains just look at the screen shot for both live writer and messenger I am currently using:
Well the new Live tools only support vista or higher. Meaning if you are on windows xp or anything below windows vista. No chance for you to test it out hahaha. As for problems… not sure as I just started using this new stuff today. Will post about it if I find any..