To each his own, of course, but my personal take is that burning DTD pretty much negates the entire point of owning a DVD/HDD recorder: if you were going to do that anyway, may as well have bought a VHS/DVD combo unit.
The added disc capacity in DTD mode cited by wajo is negligible to me except in very rare circumstances of specific movies where I absolutely do need that last possible 30 seconds to avoid dropping down from SP speed. Otherwise, any real-time sustained use of the laser for DTD recording is sustained use of the laser: again defeating a key advantage of using a DVD/HDD recorder (very brief laser use during high speed copy from HDD prolongs the laser life enormously).
I don't find I save much time going DTD vs HDD>DVD: it takes two hours to copy a two hour VHS anyway, another 18mins for the disc dub doesn't bother me and I like having the backup of the HDD recording in case the disc burn fails (you wanna talk wasted time, how about having to run the entire tape dub over again because the disc fails to finish burning or won't finalize)? As dare2be noted, more often than not you're gonna wanna put at least a couple custom chapter marks and trim junk from the beginning and end of the tape, which you can do very quickly on the HDD but very clumsily (if at all) DTD. We used to make excuses like "oh well, with VHS we had no editing options anyway so no big deal with a straight-across DTD dub" back when DVD-only recorders cost $500 and DVD/HDD was $900, but if you bought a Magnacox DVD/HDD for $200 it seems rather counterproductive not to use the HDD feature.
Regarding the 8x DVD-Rs, these aren't as crucial with the Magnavox as they are with older "classic" recorders (the Mag has a more "modern" burner that actually does have a slight clue how to burn 16x media without tearing itself to pieces). But do avoid "bargain" 16x media: it isn't that difficult to find good-quality Verbatim AZO 16x in better stores or online (stay away from the Verb 16x "Life" series now being blown out for pennies at superstores: it isn't "real" Verbatim media). There is still an advantage to 8x in terms of better burn quality because it more closely matches the top speed of the Magnavox burner, also it is more durable media for archiving, but you can do fairly well with 16x in the Magnavox. There have been scattered reports of it failing with crummy 16x media (i.e., any 16x besides Verbatim AZO), especially cheap poorly-formulated +R varieties.
I would not count on the "friendly Funai" parts situation very far into the future. People are already having a hard time getting replacement remotes from them, and once the last Magnavox blows out of WalMart I don't think replacement burner are going to be all that easy to obtain. If you can afford to, get a spare burner now: at the very least, don't go further down the media food chain than Verbatim 16x AZO.