Hmmm, I took a quick look at 2.5 over the weekend (not spent too much time with it yet) and I have to admit I am almost completely lost ATM and not entirely impressed so far!
Other than Blender and Wings3D, I've not really used any other 3D modelling software; so I'm not really sure how it compares to other high-end packages (maya, max etc). But I'd only just about mastered where everything was with the older versions of Blender and finally managed to get my head around the workflow. So my main gripe with 2.5 so far is that I have to relearn how to access all of the functionality I require, 'cause the interface is waaaay different. But hopefully taking a look at the new documentation and having a bit of a play will resolve that issue.
Other than that, the only other gripe so far is, much as it looks pretty neat the way it animates between views (e.g. when you switch from top view to front view), personally I'd rather just go straight to the required view rather than having to wait for it to animate into position each time. I think that will get really annoying after a while. Hopefully there's an option to turn the animation off when changing views.
Ultimately, I think I need to spend a bit more time with 2.5 before I decide whether I like it or not, but at the moment I'm still very much in favour of the old interface.
Cheers for now,
Jas.