The space taken up by a 30minute show depends on the recording quality you pick, which is completely configurable.
For very high quality, assume anywhere from 1.5GB - 3GB per hour.
I use a 2.5GB/hr setting that has held up quite well, even through the complete NFL season.
For a glance at the default qualities:
http://www.snapstream.com/Support/Support_PVSFAQ.asp#s3sb1a3
Yes, you can skip commercials. BeyondTV uses what it calls "SmartSkip" to analyze recordings and flag commercials. When you're watching a recording, its a single button press to skip the entire block that it flagged as a commercial.
While you're watching time-shifted tv, you also have a 30-second skip button (30 is the default, can set it to be whatever you want) to skip over commercials as you go.
The Hauppage PVR-150 @ circuit city -
http://www.circuitcity.com/ssm/Hauppaug...sm/oid/99358/rpem/ccd/productDetail.do
Currently $60 after $40 in mail in rebates.
Alternatively, if you're only recording basic cable/antenna: the Hauppage pvr-150mce @ amazon is a good deal -
http://www.amazon.com/exec/obidos/tg/de...462518?v=glance&s=electronics&n=507846
Currently $63.64 with free shipping.
The PVR-150 is the card included with the first bundle you looked at, but it will come with a few extra excessories that you won't use. The PVR-150mce is a variation on the card (uses the same hardware, just different connectors and no accessories).
My HTPC uses a PVR-250mce and a PVR-150MCE, I've found them both to be quite excellent.