vasquo:
You can get one for 1/3rd the price, with 3x the bandwidth, and 2x the number of channels (4ch vs. 2ch) vs. the Rigol.
All of which is overkill for most people doing Arduino stuff, especially a beginning scope user.
There's also the fact that you never really know what you are getting via Ebay on a scope deal - how calibrated the scope is, whether the focus works or not, etc; a lot of things that are better - when buying a used scope - to try out (or have a knowledgeable friend try out) before you purchase the scope.
...and - if that scope doesn't come with probes - you might end up spending a good amount of money on a quality set of probes to match the bandwidth.
I'm not knocking on getting a used scope - but I wouldn't do it without being able to "hands-on test" it myself (which requires some knowledge about how a scope works, of course). It's just too easy to buy a pig in a poke otherwise. I have two scopes that I purchased used; I was able to test both before I bought them: one came from Craigslist - a Tek 2213 (which would actually be a great beginner's scope), the other was a Fluke PM3380B combiscope (which is a pretty neat scope all on it's own).
The thing about the Rigol and similar low-cost DSO scopes is that you are getting something new and calibrated, sight unseen - if you have no way to test a scope (or knowledge, or a friend) - it's probably the better way to go.