Top non-partisan political analyst Charlie Cook takes a stab:

Today, while there certainly will be an air of excitement for the new members of Congress and their staffs, the mood around Washington is one of foreboding, with both parties girding for very tough fights. Democrats are understandably depressed over their disappointing election showing. And Republicans, while having much to celebrate with gains in both the House and the Senate, face challenges in the coming months that are enough to quickly sober any politician and dampen any party atmosphere.

Among the numerous battles Cook forsees three major fights over the next two years:

• Judicial filibusters an the possible nuclear option
  
• A tax overhaul
  
• Social Security

Capitol Hill won't be quite as awful as it could have been, however. Cook writes,

The gloomy forecast does come with one potential silver lining, though: House Republicans on Monday backed away from earlier plans to soften ethics rules. That move, if it had gone ahead, would have come at a political and public relations cost. And it would have forced them to swallow some of their reform statements from the late 1980s and early 1990s, when it was an arrogant Democratic majority in control and an indignant -- and quite justified -- Republican minority crying for reform. I remember being extremely sympathetic to Republican cries for change and efforts to shame the House Democratic majority a dozen or more years ago. That made it harder for me to accept both lame Republican explanations of changes they wanted to make to ethics rules as well as Democratic outrage at the cavalier manner of the GOP majority.

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