The package is a Faraday cage with some magic to make it invisible. The former point is there to stop scans. The latter to stop magical examinations. When opened, the little transmitted inside it goes beep and tells Mrs Drone to release Mr Missile to come to the rescue. If the PCs open it before hand, then the missile goes to where they are. This gives the PCs some change to flee before the missile arrives. Thus you have no need to have a super stealth bomb that is shoddy and does not work. In addition, it should scare the PCs that the opposition has access to military drones.
The major changes I noticed between the two editions are as follows:
Limits prevent characters from being overly min-maxed. Each of them is centered around an attribute that is typically dumped in normal characters; the most important attribute for the physical limit, for instance, is Strength, though other attributes weigh in they have the same impact as Strength does alone. This means that you can't build a "never gonna fight close quarters" build and just dump strength and expect to do well in other physical areas, encouraging a well-rounded thing.
Mystic adepts get a huge buff. I'm not exactly sure that this is a bad thing; they still can't astrally project, but they get the powers of both mages (other than astral) and phys-ads pretty nicely. Were they still using the BP system, this would be a flaw, and I'm not sure about allowing them as the third pick on your priority system, but I think the reason that people are upset is because they don't astrally project as much as they should when not a mystic adept.
The priority system really makes things a lot better. It prevents some of the worst cheesing during character creation (don't get me wrong-it's still possible, but you have to know what you're doing and make some sacrifices).
Combat's been changed rather heavily on the bookkeeping, but not so much the execution. The Accuracy limit keeps pistols from killing Great Dragons, which is a nice touch, but also discourages just dumping into the newly increased skills and maxing them out right away. It also makes smartlinks a more tangible advantage, as do laser sights. Armor is now a single rating for stun and physical, which makes it a lot easier for new players to understand, and, in my opinion, more realistic.
Hacking's a lot better. Mind you; the wireless thing contains some logic holes and gimmicks with the new benefits it gives stuff like cyberware or laser sights, but hackers can enjoy a target rich playground with new rules for hacking that make prepping a hacker 90% easier and playing one about 50% easier; GM'ing hacking also became a lot easier. In addition, some of the more broken technomancer stuff has been revised so you now have a reason to play a decker instead of a technomancer every single time.
All in all, it's faster and more streamlined. If you want my "reviewer" version, you can check it out on my blog, but I've said pretty much everything I said there here, only without the sales pitches.
Best Answer
Leylines are covered by the magic core rulebook 'Street Grimoire'(p.35).
They are a special type of so called Mana Lines and do not work exactly the same like in Shadowrun Returns.
In the tabletop magicans may encounter magical phenomenons which produce background count. This is a positive or negative number affecting the magicians dicepool. Mana lines of all different types are concentrations of mana which result in specific background counts along those lines.
Magicans (especially geomancers) can allign and manipulate these lines to gain benefits (including better spellcasting) or to diminish the benefits another magicians might gain.