1. I'm talking Microsoft clients here. There's always going to be plenty of non-standard/genuine options but at the flick of a switch, you could be left in the dark... as for the standard MSN Messenger- I'm still using my 7.5 (which I guess could be turned off at any time too?) with Msgplus and the relevant mess.be patch and I find this is perfect for my needs. I think the new WLM has a nice interface but probably a bit too "full-on" for me. The Mac one is just crap in comparison.
2. Anyone who thinks iWork or Microsoft Excel for Mac is comparable to the Windows counterpart is dreaming. I've tried using both of these and none of them are as smooth/fluid as the Windows versions for some reason. That's before you take into account quite a few features which aren't available in terms of advanced data analysis which I use for investment analysis/modelling.
Like I said in my above posts, I love using my Mac when I can (heck I've bought two current-ish ones running SL) and am an active iTunes user/iPhoto/etc..., but even as a Mac fan, I accept there are some programs which are still better on Windows.
ps. I'm still a Mac fan even after getting a splinter in my Macbook.