[beowulf_of_wa]

i'm having a bit of difficulty explaining to a player about the differences and changes between  SR1,2,3 and 4.

anyone have a short description of each (flavored by use and hindsight?)

[CitizenJoe]

1st Ed:
Armor counted as automatic successes rather than reducing power of attacks
Attacks had 3 features Power, damage and staging (the number of successes needed to reduce or increase the damage level)
You had to roll randomly to determine your metahuman allergy.

2nd Ed:
Armor reduced power of attacks
Attacks shifted to just power and damage. 
High staging attacks just upped the power level.
You could pick your allergy
Introduced Adepts (partial magic)

3rd Ed:
Complimentary skills were introduced and some pools were modified slightly in calculation.
Priority system changed slightly
Allergies became a 'flaw'
Reach changed from -1 TN for your attacks AND +1 TN for opponent's attacks to OR.
Equipment became upgradeable rather than having to replace the whole thing.
Build point system option for character creation

4th Ed:
Complete reworking of the dice mechanics.
Skill tests were stat + skill instead of just skill tests
Skills changed and regrouped
Some Attribute changes
Build point system standard ?
Significant change in setting
Much of the nitty gritty details were left out to streamline the game
Magic system and spirits reworked.

[Ajax]

CitizenJoe handeled the mechanical differences very well, so not much for me to add.  The various editions all had differences of flavour and fluff as well, each being "70 years in the future" from their publication date, but still being a product of their time. For what its worth, I'm attempting a "revial" of 2050-era Shadowrun in another thread, modern rules, old-school style.