So unless Scala has some secret ingredient to use the JVM more efficiently, this looks to me as yet another fanboy rant.
Secondly, any "ranting" you hear in this article is the product of El Reg, not Alex. He mostly offered a calm, positive presentation about the improved speed (with relatively little, if any, tradeoff in developer productivity) that came from using Scala instead of Ruby for critical infrastructure services.
Regardless, most Java web applications' performance issues stem from framework-itis, not from the underlying runtime. By itself, Tomcat (or another modern Java servlet container) is capable of some pretty impressive throughput -- perhaps not on par with a lean, pure C server like nginx, but not nearly as limited in functionality and extensibility, either.
No matter what you think about Java the language, you at least have to admit that HotSpot blows MRI, YARV, the Python VM, and Parrot out of the water when it comes to raw performance on low-level code. That doesn't save you from bad implementation ideas, but it does at least give you the possibility of getting fast, efficient code, if you have a decent compiler and work fairly close to the metal.
Using Scala is one way to produce that sort of low-level implementation code without wanting to gouge your eyes out (which is how most Java source tends to make me feel, anyway).
The rest of your comment, you change what I said so it's not worth addressing.
> Java scales just fine thanks. FWIW, Mibbit handles a good number more messages
> per day that twitter. On a single VPS with 1.4GB ram, running Java.
Third time lucky, I hope. My point is I seriously doubt Scala is much better at scaling than Ruby, Python, or PHP. And the author seems to have based his opinion on his experience refactoring Twitter components previously coded in Ruby in Scala. Caveat emptor, I wasn't at the conference and this rant is second hand via a questionable source, The Register.
I spoke with some people at Twitter the other day. They said that they were switching to Scala just to annoy alecco on Hacker News. The performance and scaling advantages are entirely negligible.
I don't get the sense that they are that inexperienced. If they think a switch to Scala will handle more volume, I'd be really shocked if they didn't have some solid evidence to back that up.
> Careful here: are you _really_ suggesting that Twitter would do a full rewrite
> without making sure that it would increase throughput first?