It's been a long time that I've been thinking about buying a loop station.

The main reason that I want a looper is to practice at home - soloing and composing. That's where the ease and quickness of the looper really comes into consideration.

Another thing I would like the machine to be is some sort of a multi effect - doesn't have to be, but would be awesome. I have no pedals at all.

My budget is around 500$. If you have a machine that you think worth the extra cash (100$ more), let me know.

I thought about the Line 6 JM4. Any comments about it?
I'd be happy to hear any suggestions for loopers to explore.
Check out the Zoom G3. It has a very easy to use looper, drum track metronome, all kinds of crazy fx, sounds good through headphones. Less than $200. If you want an expression pedal, get the G5. They're both superb practice tools.
Fender Mustang/Derfenstein DST> Boss Power Wah> Pedal Monsters Klone> Bogner Uberschall> Walrus Audio Janus> Randall RM20> Line 6 M9> Randall RM20
Definitely the Zoom, but go for the G5. It has 60 sec vs the 40 in the G3. The Zoom series has a synced drum machine, so it works with the looper. They also have a progress bar that really helps you get track of where you are in the loop for overdubs, and how much time you have left when recording the initial loop.

The JM4 is probably more suited to just jamming as it has backing tracks installed. I actually just ordered a used one from GC for $115 shipped with tax. It's not mint and lacked the P/S, which I have a extra handy.

You should also use some kind of recorder if you want to save your ideas. Otherwise you need to get a looper with storage. The Jamman stereo is a decent looper with storage.

If you want something really unique look for a used GNX4 on eBay. It has an onboard 8 track recorder/looper with synced midi drum machine. Plus it's a full multifx with XLR input for a mic. The multifx itself is a bit dated but serviceable. In addition it can play MP3 backing tracks. It's an incredibly powerful device. You can even reamp a guitar track on the recorder.