That would be unfair for game devs who made it through and making money just using the free version. It does lack features vs Pro but it is still viable for a production release.
Yes, it is certainly viable and I don't mean to discount what Unity offers for free. However, IMO the restrictions matter as in, for instance, the free version does't come with pro's lighting and shadow etc. GAme devs do resort to small "hacks" to get around but it is a slight inconvenience at the least.
Either way, doesnt hurt to have competition :)
A minor clarification, Unity Free does have real-time lighting, just not real-time shadows.