Personally, I'd never given it much thought since I have a rental server contract and my company of course provided me with space, but since around last month I've been playing around with something called InstantWordPress.

What is InstantWordPress?

It's a tool that lets you try out WordPress in a local environment (on your own computer) without having a rental server contract. It's handy when you just want to give it a try, when you have an existing site and are building a renewed version alongside it, or when you're juggling multiple site projects—you can split the projects across USB drives and work on them separately. And in my case, since I also teach WordPress at a school, I wanted to test it out so my students could use it.

1. The WordPress version is old
You can upgrade from within the admin screen, so I recommend updating to the latest version after downloading it!

2. It's just plain slow
I suppose it can't be helped since everything is running in a local environment, but as someone used to working at a brisk pace, the lag made it feel awkward to work with.

3. The PHP version is old
I found several plugins that weren't supported because the PHP version was too old. Whether downloading PHP would make them usable is something I'd like to verify when I have time.

4. File edits made outside the admin screen aren't reflected
Because you're working in a local environment, when you edit files directly, apparently the changes sometimes aren't reflected depending on the location. Files accessible from Appearance were editable.

5. Mac users can't use it
It doesn't support the UTF-8 character encoding, so it can't be used on a Mac.

6. It won't launch if the computer user name uses full-width characters
When I added a new computer user and registered it with half-width alphabetic characters, it launched fine.

I'd casually assumed that as long as I carried a USB drive around, I could try it out anywhere—but the last issue I mentioned was the one I really struggled to solve.
I've only listed the inconveniences here, but it's a very handy and genuinely fun tool to use, so I plan to keep experimenting with it.