Sovereign casts Increase Attribute: Charisma [4 hits on 14 dice for spellcasting, 6 hits on 18 dice for drain vs. 6 drain], taking no damage and sustaining with focused concentration. He follows up with Increase Attribute: Willpower [5 hits on 14 dice for spellcasting, 8 hits on 22 dice for drain vs. 6 drain], taking no damage and sustaining with focused concentration. He finishes with Increase Reflexes [buys 2 hits, 7 hits on 22 dice for drain vs. 6 drain], taking no damage and sustaining with focused concentration.
I wanted to recap this, but instead of considering what Lormyr's players actually rolled, I want to look at probabilities. So consider Sovereign from Lormyr's example above. I'll recap his important stats here:
Base drain resist is Cha 9 + Wil 5 = 14 dice
Sorcery(Spellcasting) = 6(+2)
Magic = 6
Essence = 6
First, he casts Increase Attribute against Charisma. This rolls Sorcery + Magic (5-Essence), giving +1 to the selected stat per net hit. The drain is 3, +1 per hit beyond the first
Spellcasting test: 14 dice vs (-1) gives 89% chance of 3 hits or more (and can buy with autohits if GM agrees), plus the 1 "free hit" from Essence. He's only one die away from buying a guaranteed success that gives the maximum +4 to the stat.
Now the drain resistance test. Lormyr appears to allow the +4 Increase Attribute to be included in the drain roll, which feels slightly generous but is (I think) RAW based on the "all spell effects happen even if Drain kills the mage". But let's be extra harsh and say that it doesn't, though. That would make Sovereign roll 14 dice vs (6), giving drain chance of:
0 boxes: 31% chance Sovereign resists all drain
1 box: 52%
2 boxes: 74%
3 boxes: 89% (can buy this with autohits if GM agrees)
If you allow the Increase Attribute to apply to the drain test, then the 31% chance of no drain becomes 59%.
Now repeat with a second casting of Increase Attribute, but with +4 dice against drain now due to the first Increase Attribute being in effect. No sustain penalty due to Focused Concentration. I'll assume no wound penalty; there's only an 11% chance of 3+ boxes of Stun damage from the first spell by the "harsh" version of the rules.
Spellcasting: the same 89% chance of getting 3+ hits as before.
Drain: 18 dice vs (6): 59% chance of taking no drain at all. 97% chance of taking 3 or fewer boxes. If you follow the "Increase Attribute takes effect before drain" reading, there's a 79% of no drain at all on this second spell.
Now for the Increase Reflexes. Same Sorcery + Magic (5-Essence) test, with each hit granting +1 Reaction and +1 dice. Base Drain Value is higher - 5, +1 for each net hit beyond the first.
Spellcasting is the exact same 14 dice test, but let's break the probabilities down a little more:
Chance of 0 hits: 0.3% (this still gives +1 Reaction / +1d6)
Chance of 1 hit: 2.4% (+2 Reaction / +2d6)
Chance of 2 hits: 7.8% (+3 Reaction / +3d6)
Chance of 3+ hits: 89% (+4 Reaction / +4d6) (max) (can also buy this with autohits if GM agrees)
So there's a good chance that Sovereign can get the max +4 here. Now consider the drain resistance chances, with 22 dice, against a maximum drain of 8 (5 base, +3 for applying 4 hits; this assumes the "free hit" from Essence is included in the drain calculation although that isn't clear to me.)
Chance of 8+ hits: 45% (with no drain, this would give Sovereign 14+5d6 initiative and 1 Major/5 Minor actions)
Chance of 7 hits: 17.8%
Chance of 6 hits: 15.6%
Chance of 5+ hits: guaranteed (can buy this)
With three chain casts -- at most, ten seconds of prep time - Sovereign can all but guarantee casting all three, with reaction time equivalent to Wired Reflexes II (which costs 150k nuyen and 2 essence.) If he's unlucky, he might take a couple of boxes of Stun damage. But if he's just a little bit lucky or prepared to use some Edge or reagents, he can pretty easily get up to the same level as Wired Reflexes IV (400k nuyen, 4 Essence.)
You tastes may vary, but if I'm a Street Samurai at this table who's invested in massive amounts of expensive 'ware to get the same effect, I am feeling short-changed at this point.