Are you asking this question because you are making a technology decision for a large web site? Whilst Microsoft has been coy about recommending it for large sites, I don't think you'll have any problems that can't be solved if you structure it sensibly.
As always the context of a technology choice is important, for example if you are displaying a large number of disparate data sets in your views for a heavily data-centric site then you may find that your controllers and views get a little complex and "busy", but you'd also have a similar problem in your code-behind if you were using "Classic" ASP.NET.
But if you are simply asking "Is it solid and scalable?", I'd be inclined to answer "Yes".