First of all, I never played the boardgame or the SNES game before I tried Shadowrun Returns. I guess this is important because some people say it doesn't have that old-school appeal. However, I can tell you this is an amazing game with great storytelling and some of the coolest atmospheres I've ever seen in a game. Basically it's noir fiction set in a cyberpunk multiracial world (elves, humans, dwarves, orks, trolls) where magic and technology are used everyday.
The gameplay is very flexible: in many missions you can choose a team and you can include hackers, drone masters, berserkers, spirit summoners... so if you want, you can go and shoot all the enemies with your team members, or you can send some drones and spirits to do the dirty job. The character progression is decent: everytime you accomplish an objective you win some points that you can use to upgrade your skills. In my gameplay I had an sniper shaman with a decent amount of healh points and some basic mage skills, so as you can see you can have any combination you want.
The main flaw is the checkpoint/save system: you can only save after you finish a mission (and it's an automatic save). In average, each of the missions can last from 20 to 40 minutes, so it can be pretty frustrating to die in the middle of a battle and have to repeat all over again. Apparently, this issue is going to be fixed by the developers with the release of the new campaign next year (2014). Also, you could find some minor bugs in the game. For example, I had to repeat a battle because at end of it there was a conversation and suddenly it stopped and I couldn't advance to the next mission.
Finally, you have to take into account that the game has Steam Workshop support! There are some projects with new campaigns. For example, some people are trying to bring back the original Shadowrun SNES campaign. I haven't tried them yet because I'm waiting for the finished version. However, I believe the user-generated content will increase the value of the game in the medium/long term.