So, I played a lot with friends since the release (I believe we already have 20 hours in).
Stealth : it's relatively easy how to do it, but things can fuck up that you simply can't control and are fucking annoying, like random civies on the street, that spawn and call the cops out of your range, and without an exclamation mark. Civies that are not synchronised for each player (once had to tie a civilian that every player but the host could see). Though, honestly, we're making so much cash, killing civies is an option right now (e.g. we always kill the bank manager in bank heist, it's so much easier to put him in a bag). Also, you're still quite stealthy with max armor and big weapons (have a friend that goes take the keycard in the manager's office in bank heist, and he's not ghost), so I always take max except when I do jewelry or bank heist and take suit (depends which bank heists). The only one where random shit don't happen is nightclub (until the point where you have to move the cash, but that's ok) which is easily doable in solo. FBI and the Senator's flat are the hardest to do stealthily imo (but those extra bags are so sweeeeeet).
Not being able to point guards and stuff like that in casing mode is stupid too.
Cash/exp : right now, we are making lots of cash, but exp is getting harder and harder after level 30, we only get 1 level from a mission (pro very hard, generally). I have 2 millions cash unspent, having bought all the mods I want and have right now, and I have 4 primary weapons, and 3 secondary.
Skills : going for the technician tree, but without the sentry, took some useful skills in other trees, such as fast loot bag interaction, faster transporting speed, etc (basically, most loot bag skills are worth it). Completely silent drill is useless, the semi silent is enough, you'll be caught for something else anyway (if you get caught). Skills to decrease costs and such are useless imo too, but that's because we're making shitload of money (last mission was 300k on a bank heist). From the beta, the sentry is meh, the only reason I could use one is to slow down cops going after us, but that's situational, and not worth investing lots of point imo.
Apart from a few select skills, I'm not sure Ghost is worth it. Fast hands is mandatory for everyone, but apart from that, you only need one person to lockpick/ecm open door, and you could do that with a semi silent drill.
Throwing bags further is awesome and hilarious, and having a saw in your group is really helpful for a lot of mission. It's meh that you have to sacrifice your main weapon, especially for a combat oriented class, but it just can be amazing (will compare to the C4 once I get it, but you can't reload C4).
Having a mastermind with heals in your group is mandatory if it's a mission with fighting. 2 bags worth 4 uses each is nice.
Weapons : I really like how it works, and the mods. Some mods are meh (or other mods are simply better), but I like the system, and just wish there was more weapons and stuff. I like the JP36 especially, and the Mark 10 is a really good combat oriented secondary, despite being a low level one. High damage with one of the fastest rof. I am currently testing the AK-5, which is nice, and the AMR 16 seems good, though with not much ammo.
Had an annoying bug recently, where in the second day of Rats (the trade for the information on the Mendozas), the arrow pointed to an apt where the info wasn't, and the gangsters gunned us down as we entered. Was Pro, so we had to drill all the safes, to finally found it in another apt block.
There was some crashes and lag at the release, but it seems fixed, so yeah.
Also, you can take bags and generally interact through a wall, it can be very useful, like in Day 1 Firestarter.
Overall, it's a really great game, and a really nice improvement over the first. I know some people are dissapointed, but I guess not everyone likes the genre.