QUOTE (Doc Chase @ Oct 7 2010, 02:29 PM)

I thought the rules were fairly clear that if Essence < 1, then Magic = 0 despite the number of initiations.
I suppose I'll have to go through them again to verify.
No, SR4A made it clear that if your Essence went below 1, the major effect is that you've lost a point from Magic and your natural maximum Magic was also reduced by the same amount.
Essence.......Magic...Loss
..6.00-............6.........0
..5.99-5.00.....5.........1
..4.99-4.00.....4.........2
..3.99-3.00.....3.........3
..2.99-2.00.....2.........4
..1.99-1.00.....1.........5
..0.99-0.01.....0.........6
What Initiation does is raise the natural maximum of Magic by +1. The only caveat is that you cannot Initiate more times than your current Magic attribute.
Now heading to sub-1 Essence is the path of the burnout as many burnouts don't initiate. No initations = burnout when your Essence drops below 1.00. If you want to avoid being locked from further magical progression, you have to stay at Essence 1+. That requirement aside, there is a crapton of stuff you can implant within 5 Essence.
You can see the relevant sections in SR4A Rev 1. For ease, I've copied the excerpts from the PDF.
CODE
SR4A Rev 1, Page 68
Essence Rating: All characters have a starting Essence attribute
of 6. Cyberware and bioware implants reduce this rating. No character
may start with an Essence greater than 6. Under basic Shadowrun rules,
characters can never have an Essence of 0 or less. If they do, they die.
Characters with Magic or Resonance attributes are subject to penalties
if they have an Essence lower than 6. For each point or partial
point of Essence below 6, the character loses 1 full point from her Magic
or Resonance and the maximum for that attribute is reduced by 1.
The maximum rating for Magic is 6 + initiation grade (see Initiation,
p. 198); for Resonance the maximum rating is 6 + submersion grade
(see Submersion, p. 243).
Now for the section on Initiation...
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SR4A Rev 1, Page 198, Under the heading Initiation
A character’s initiate grade cannot exceed her Magic attribute. If
a character’s Magic is reduced below her initiate grade, she loses that
level of initiation and the metamagic she gained with it.