Honestly, it's not really that overwhelming of a tactic. Casting a spell at Force: 1 is one whopping point of Drain less than a Force: 5 spell, at the cost of 4 points of base damage. It's better to use Edge to boost normal casting, rather than expend such a finite resource to make a weak attack slightly better.

it gets much better when you are (for example) using a rating 1 sustaining focus (IMG:style_emoticons/default/wink.gif)

I'm not interested in resurrecting a discussion that got disabled by the admin, but there are a body of DSers who argue that if you add Edge dice to a glitched roll and doing so raises the total number of dice to more than twice the number of 1s then the test is no longer glitched.

For example - on a Force 3 spell you roll 1, 1, 1, 3, 3, 4
That's a critical glitch, but fortunately you have a healthy Edge of 6.
So you roll 6 Edge dice and get 1, 2, 5, 5, 5, 5
The roll is now successful, is no longer a glitch and has more useable hits than the Force of the spell.
Three things for the price of one.

I'm not saying this is RAI, or that it's the best interpretation or that it's even my interpretation, but it can and has been interpreted that way.

Two points less. Half of one, rounded down, is 0.

There is always a minimum of 1 Drain. So no... (IMG:style_emoticons/default/smile.gif)

That's for total drain value, so while a stunbolt should always be cast at a minimum of F5 (barring extreme cases where you doubt you can resist 1 drain, and it would be overcasting), it makes perfect sense to do F1 Increase Reflexes (DV 2 at F1, where it would be DV 3 at F3 and so on) with edge for sustaining foci.

Without a doubt... AS long as you don't mind losing your Foci upon entering a Rating 1 Background count. Sucks when that happens, and it happens fairly regularly.

I hope you're considering adding Edge dice to that Force 1 Increase Reflexes spell when you cast it, otherwise you're not gonna meet that Threshold 2 for the minimum benefit of +1 Initiative & +1 Initiative Pass. (IMG:style_emoticons/default/spin.gif)

And what TJ said. Rating 1 Ebbs/Domains aren't all that uncommon. Worse thing that could happen would be to wander into a field of flowers and find yourself in the middle of a Rating 3 Ebb created by those flowers (the name of the plant that does this escapes me at the moment).

The other thing to think about is wards, which are also fairly common. For a mage using a sustaining focus normally, it is fairly simple to end the spell, go past the ward, then recast it again (although having to resist Drain again is an annoyance). A mage relying on Edge to have the spell functional at all, though, would have to go through a point of Edge every time that happens.

Indeed... Never worth it in my experience. (IMG:style_emoticons/default/smile.gif)

Oh, I don't know, could come in useful if a squad of Red Samurai were about to corner you ... but yeah, I would consider using Edge in sustained spells wasteful as a SOP, due to danger from ward or perhaps BGC (for low force spells/foci) disruption.

But as you said upthread, at F3 or even F5, use of Edge to exceed the F hits cap can be pretty useful. One of my players started with a MAG 3 human mage with Edge 6, and boy he could sling the mojo when he needed to!

No doubt, but I bet he did not sling it into the Foci. I had a similar character, Magic 3 Caster with only an Edge of 3. The vast majority of his spells did not require hits above 3 (He had no combat spells at all), but the ability to use the Edge to bypass the cap on those rare occasions it was needed was handy indeed.