I'm still processing the new rules (and having gotten around to a close reading of it all yet), and the book DOES weigh in at 480 pages, but a summary:
- Limit mechanic introduced; almost every test you roll had some defined limit for how many hits you may count on a test as seen in SR4's Spellcasting
- - Many dice pool bonuses are changed to limit modifiers; dice pools overall are smaller as they're very nearly always only Attribute+Skill
- - This actually makes the sheer amount of guns that are around have more of a point, too.
- Wireless bonuses added to many items; in essence, a bonus is confered for having gear connected to the Matrix (the reason for this is related to the Matrix changes; essentially, you can still go completely offline but the decision is now more complex than "turn hacking to off"). There is an issue in that they first converted most dice pool bonuses to limit modifiers then put those dice pool bonuses back in place with wireless on, which tends to create a certain perception.
- Initiative changed such that number of passes is determined by your Initiative Score, there are ways to "spend" initiative points to do things like get a bonus to defend against a melee attack or to intercept someone passing within 1+Reach meters.
- There are many cost adjustments with 'ware, in terms of both nuyen and Essence
- - The "half Essence for the lesser of cyber/bio" rule is gone, but bioware Essence costs have dropped notably
- Edge has a static default refresh rate of every in-game day
- Matrix rules entirely redone, new system is simpler but also more punishing to hack; in setting it means a lot less hackers are actually going to be around
- - Some of the technomancer changes are... Questionable would be putting it kindly.
- - Matrix given a notable direct role in combat; Matrix Damage now goes to the device rather than merely to an icon,
- Riggers are back to being their own dedicated character type, Deckers similarly have an increased barrier to entry
- Adepts can now get qi foci that actually give them more powers, mentor spirits now have benefits ascribed to all Awakened, to Magicians specifically, and to Adepts specifically (usually free powers). Augmented/Unaugmented Adept balance appears to be a lot better
- Skills go to 12, with chargen caps being 6 (you can have as many as you like at 6)
- Attribute balance adjusted so that less important Attributes in SR4 become more valuable
- Damage and armour is scaled up, but overall damage has increased, reportedly making for a marked increase in lethality
I'm definitely missing stuff, but this is what I can think of for a rundown right now. The rules overall are pretty similar (they've said that they built from the idea of taking what worked in SR4 and fixing what didn't).
Notably, I'd have a hard time converting Fionn at present for the simple reason that he's not using the default stream, but one of the ones from Unwired - two of the Technoshaman sprites aren't in SR5 as yet (Paladin sprites, which serve a far more important role in SR5, and Sleuth sprites, of which I've made extensive use). That, and some of the changes (especially in regard to sprites) make it questionable as to whether the concept of how the character works can really convert over.