speaker simulators

Yes, it works fine.

The results are VERY close to the sound of your amp via the Speakersim.

I did this with the speaker sim of my Koch Studiotone and the sound was spot on.

You have the option to select another real cabinet later - in the KPA - this may sound even better than the speaker sim.

IMHO does the real amp profiled with the real speaker sound best - but this needs a lot of additional gear, a large room, a lot of noise and some knowledge - to capture the amp with e.g. a palmer is very easy.

there are a couple of rigs in the rig exchange that were made with a speakersim.

also, the character control in the cab section can be used to turn a regular cab into a more speakersim-like sounding version.