The Magnavox 513 and 515 are virtually identical aside from 320GB HDD on the 513 vs 500GB on the 515. The 515 also has a nicer remote and the ability to pre-name recurring recordings (i.e. if you record "Two And A Half Men" every week, each one on the HDD will automatically have that title- the 513 will not do this, it records every show with a generic time and date label which you need to manually change). Both Magnavox models will let you name individual recordings any way you like, and you can edit out commercials or split long marathon recordings to smaller chunks. Hard drives are fairly easy to swap, so you can have separate HDDs devoted to different types of recordings (depending how ambitious you are). Unfortunately the process of entering title names is extremely tedious (it uses the cell phone number pad system from ten years ago), and you can't do much organizing: the file system is strictly top-level (no groups or subfolders).
Whether you would like a Magnavox better than Replay or your Comcast PVR is an open question. I am on record here, and somewhat vilified, for saying the Magnavox is kind of a pointless purchase unless you specifically want to make a lot of DVD archive copies of stuff you record. If you want DVDs, this is your box: its one of the nicest DVD/HDD recorders ever sold and its very affordably priced (esp the 513). However: do not assume it will work as easily as the Replay or the ComCast PVR. The Magnavox is not the least bit integrated with cable, its "cable-compatible" tuner is only partially compatible: it assumes the cable company will not screw with the specs, but the cable companies always screw with the specs, so you have to reset it frequently. It also will not pick up any scrambled "standard" or "premium" channels like TCM or HBO: this requires you still use the decoder box, and switch timer setting between the Magnavox tuner and its line inputs (plus set the timer on the decoder box).
Getting the picture? It isn't exactly a joyride to use. This is not the fault of the Magnavox, all DVD recorders have these conflicts with cable: its a problem with cable doing everything it can to discourage people from using non-subscription hardware. The petty annoyances are worth it if you want to make a DVD library, or HDD swap library, but if you don't: whats the point? The ComCast PVR or TiVO are much easier to use. They get all the channels without futzing with a dual hookup or separate decoder, they automatically follow the cable company channel reassignments, and they can record in full Hi Def (DVD recorders are limited to SD, which from cable does not look so great on screens over 37").
The best advice is to buy one from Wal*Mart and give it a test drive. See if it will do everything you want it to, in a manner you can live with. If so, great: join the multitudes here who enjoy this amazing bargain of a recorder. If it doesn't work out, Wal*Mart has a generous refund policy of at least 30 days, no questions asked. You have nothing to lose but the time you spend giving it a whirl.
