As with all these types of questions, they only make sense if there is more information in the question.
If the question is,
What is one of the best editing platforms for editing a feature film shot on High Definition, for commercial purposes? Then the answer is going to be Avid Inferno.
If the question is, what is the fastest growing professional editing software? then the answer is going to be Final Cut Pro, especially for ENG, Video Documentary and low end TV production (DIY shows for example)
If the question is, what's a half decent piece of editing software for the PC? Then the answer is going to be Premiere.
The question really is, what are you trying to achieve?
From my personal point of view, I think there is a distorted view of the industry at the moment that goes along the lines of:
"If I buy a Sony PD170 or a Panasonic AG DVX100, I can shoot a feature film and edit it at home on my PC on Premiere and then I'll be able to sell it."
The only thing is, as Sonnyboo points out, there is a vast amount of difference between a $600 software package and a $75,000 edit suite; there is a massive amount of difference between a $5000 dollar camcorder and something like a Panasonic DVC Pro 50 camera which is closer to $50,000 (before you even buy the lens)
I have Final Cut Pro and imovie on my mac, I use them for messing around with hobby projects. I don't even own a mini dv camera and I do like the Panasonic AG DVX100, it's great for scouting locations and training students in basic film making (which is what it was designed for)
I think Sonny Boo is right, Avid Express doesn't compare favourably with the competition for home editing, except in the fact that Avid is the primary editing tool of professional filmakers.
If I was just starting out and intended to get serious about film making I'd definately go with Avid Express, I'd invest in a secondhand Beta SP Camera and deck. These would be the cheapest "pro" tools I could afford. I'd learn cinematography and editing on these, by making loads of short films and by seeing how my decisions translated into actual footage and then how that footage edited.
Then, after spending at least a year and seven rewrites on my first feature script, I'd shoot a simple, straight forward, genre movie, that would have direct to DVD/cable potential and I'd shoot it on Panasonic DVC Pro50 and cut the best deal I could to get my post production done professionally.
I'd borrow some Avid space/time, to do the rough cut myself and then pay a professional editor to tidy up.
I've said this before, I don't think indie film making should be about doing everything myself, it's about finding other people who are passionate about what they do.
If you want to know what the best editing system in the world is, it called a "Richie." That's because Richie loves to edit, he's creative and he makes my films better. The fact that he uses Avid is not the most important thing about him.