I use SimpleWorker for some background jobs in our Rails apps, I like the service! It's totally the only service with a really nice dashboard to see how your jobs are doing, as well as scheduling them to run. Resque is good, but I wish it had a real scheduler.
I like it too obviously. I randomly met the guys last week and learned about it, it was very simple to take my script and just make it work. In general I see the Ruby/Rails community as being very receptive to services like this (and ours).
This is neat, but what is a good use case for this? I would assume most people needing search functionality already run their webapps on a server somewhere.
There are many uses, one of them is when you want to do instant search. There is no point in having the browser go to your server so you can act as a proxy for a query.
Also, you could add search functionality without having to touch your backend logic (only your web templates). This may seem minor if you are in control of the whole web app, but it matters for larger organizations where it's easier to change a template than to deploy code.