I updated my Mac from Snow Leopard 10.6.8 to Lion. Everything went well. The computer restarted when the OS setup finished. Now, Spotlight setup has been running for more than two hours. Is something wrong? In the meantime, I can't open the App Store or Software Update.
First off - Spotlight works because it has filters that look for information within files and store those "nuggets" in a database so when you want to find something, you don't have to go search each file.
Lion changed the filters, so your entire hard drive has to pass through the changed filters. The first pass could be done in about the same time as the install took if you have nothing on the mac.
It's hard to know what type of files you have - as spotlight will take a lot longer to index a 5 MB text file than it will a 5 MB music file. Using the mac will slow down the updating, so many people turn off spotlight after an upgrade and let it do the entire drive scan over night or when you are away from the mac so it can just do that one task without slowing you down.
I would say most macs that can run lion should be done indexing in 12 hours unless there are problems. Those problems usually have messages in the console log (/var/log/system.log) - but it's probably just something you need to wait out.
Yeah, it will all depend on how big your drive is, how full it is, and if you have any other drives attached to your computer. I would let it sit overnight. It should be done after sitting that long.