They'll have to bring a hell of a lot to the table to match what the free software sims are currently offering...
While I agree to a point, I always ask myself if the "price" influences the feelings one has towards these free amp sims.
I tend to believe that most of the developers doing these sims for free would much rather, in their hearts, be making money off of these en devours and are ultimately setting it up so they can someday do just that.
As an example - Ken at ACME is looking to make the jump (not neccessarily in the AMP sim market) to commercial products at ACME. While I'm sure he is going to attempt to price his products in what he deems a fair pricing structure, ultimately he is looking to develop this into a profitable enterprise.
While people like Ongle and LePou are making free stuff right now - do they have commercial dreams and aspirations? Will you feel the same about their products when it is coming out of your wallets? Or will you look for the next great free one? I in no way ask these questions to pass judgment on anyone's intentions as I believe people should profit from their talents and would gladly pay whatever price they think their work is worth if I felt it fair and worth my investment.
I look at Amplitube as a whole product - it has modeled 160 individual items. While some I may never use, the fact that I will have them in my bag of tricks is something I value if the time comes that I'm looking for a particular sound or effect. With a current upgrade price (current presale code to owners of Amplitube products) of $149.00 and the ability to use my Jampoints to lower it even more, it seems a pretty simple choice for me. It's less than a dollar an effect, or amp, or cabinet, or rack effect, or any other ability the product offers. The new full stereo path allows you use the huge collection of analog and digital effects on your vocal tracks, keyboards and drums as well as my guitars. That's pretty cool to me.
Once again - for my use, that $149.00 will go a long way. Sure - my music is only for self consumption, but as I've noted before - I play and record for my own enjoyment and I like variety. Listening to the audio examples for Amplitube 3 got me wanting to play guitar and I think that's what the intent of any musical product is - to make the process of making music enjoyable and rewarding - something I want to do.
Just my 2 cents - your mileage may vary.