It's insanely fast. I didn't know it had even been released, but I went to select the copilot SWE test model in VSCode and it was missing and Haiku 4.5 was there instead. I asked for a huge change to a web app and the output from Haiku scrolled the text faster than Windows could keep up. From a cold start. Wrote a huge chunk of code in about 40 seconds. Unreal.

p.s. it also got the code 100% correct on the one-shot p.p.s. Microsoft are pricing it out at 30% the cost of frontier models (e.g. Sonnet 4.5, GPT5)