Fender is banking that most people aren't seeing the Rumble 40 the same way that I do. $350? When I look at what $350 could buy me I saw a huge tradeoff between power/strength and gadgetry. For $300 I was able to buy a regular Rumble 100, a TCE BG250-12, a bit more for any of their other speaker configurations, loads of amps I didn't try... and for $400, only $50 more I landed a Gallien-Krueger MB112-12 [I actually purchased the Rumble 100 and TCE, but returned them both, preferring the GK].
When I first got back into electric guitar playing and needed an amp the sales guys were all over the Fender Mustangs. I was looking at the lower end of the line and saw so many other amps that were simpler and better sounding. I should state that I thought the larger versions of the Mustangs were pretty good as SS amps go and would probably agree that it's similar in the case of the Rumble 800 studio (or whatever it's called).
The way I see it, if you have $350 to spend the choice is between a tool and a toy. I have to wonder how Fender will do with them at this price point? JMO