http://www.newegg.com/Product/Product.aspx?Item=N82E16816132015

Anyone using it? It comes with a PCI-e card and it looks like this kit contains everything I need to setup a RAID 5 system other than the hard drives...

You get what you pay for. I would be paying them a compliment if I say that the raid card is mediocre at best. Silicon Image is usually a bottom performer in raid tests.

What is another popular and better RAID 5 enclosure?

The problem is not so much the enclosure, there is an abundance of choices there, it is the raid controller and the conncetion to the PC. You have several options, iSCSI, fibre or eSATA for the connection. iSCSI with teamed NIC's is a feasible option if you have two NIC's free in your PC, for instance the Thecus line (NAS) is worth having a look at, fibre requires a dedicated Fibre controller which is never cheap. Look here: ATTO Fibre RAID Controller : (http://www.timelinedigitalinc.com/atto-fibre-raid-controller-c-97.html)
The alternative is a solid SAS raid controller, like an Areca ARC-1680iX 12 port or higher with multi-lane eSATA connectors, which means that you can connect 4 drives with a single cable. Way more expensive than the Silicon Image, but with up to 4 GB of cache and BBM (battery backup module). They are the Rolls Royce amongst raid controllers.
Another source to have a look at is AC&NC - Products - RAID Arrays - NAS - iSCSI - SAS - SCSI Cables - FC Cables (http://www.raid.com/02_00.html)

Another thing to keep in mind that I probably don't necessarily need the top of line RAID system with top of the line performance. I'm only editing Cineform 720P and 1080P files, and rarely more than 2 streams simultaneously... My criteria are: Ample space, reliability (RAID 5), decent performance. I'm guessing a Silicon Image controller is sufficient for my needs? Or maybe even a Drobo would be fine as an editing drive?

Not sure if it's still relevant, but I just noticed 3ware are giving a very large discount on some of their discontinued products. There's a link on their home page. They are more or less comparable to Areca, no?

Just about as comparable as Fiat versus Ferrari. The first one is far more economical in fuel comsumption and price, the second one in performance. It depends on where your needs are.

I was under the impression that in entry level cards, at least, they are both more or less in the same league. They are also very similarly priced. Does Areca have in your opinion such a performance advantage over 3ware with the ARC-1210/20/30/60 series as well?

I'm no expert in RAID or drives, but this one looks nice. It appears to handle all of the RAID stuff onboard so you don't need a RAID controller, only an eSATA port on your machine. Does this sound right? Or am I way off?

OWC Mercury Elite-AL Pro Qx2 eSATA,FireWir... (MEQX2KIT0GB) at OWC (http://eshop.macsales.com/item/Other%20World%20Computing/MEQX2KIT0GB/)

I was under the impression that in entry level cards, at least, they are both more or less in the same league. They are also very similarly priced. Does Areca have in your opinion such a performance advantage over 3ware with the ARC-1210/20/30/60 series as well?

This is rather dated info, but judge for yourself. Keep in mind that the Areca 1680 line, based on the IOP341, is even faster.

thanks Harm