Word of mouth tends to be far more reliable and valuable overall than "Professional" reviews. Because for the most part you can trust they're being honest to their personal tastes. Then all you need to know is what their personal tastes are (which is why you look at past reviews as well).
With professional reviews, you have to wonder if they were paid, if they're simply scared of giving a poor review to a game, or if they simply have a heavily skewed system of rating. There are groups that refuse to give anything below a 5/10 rating. Absolute garbage will get a 5/10 rating when if they properly rated it on the 1 to 10 scale, it would deserve a 3/10 at best.
Obsidian games may sometimes have warts, and while I may not like ALL their games, I have to say, they've earned a good solid reputation. I will give them the benefit of the doubt on any game they put out. If there are bugs (impossible to catch all the bugs before release), I will be more patient on giving them time to fix the bugs.