For me it's just Exeter who are way ahead, Sarries and Wasps have been much too inconsistent this season to be considered a large gap ahead of the chasing pack. Ahead, yes; but not with clear water.
Bath look pretty comfortable in the top 4 as far as squad strength on paper is concerned, but are even more inconsistent, and still trying to work out how to use their talent.
Gloucester, Leicester Sale, Newcastle and Quins all have areas of weakness in their squads which they're capable of overcoming, but handicap them in my analysis here (AKA, an "on paper" analysis)
Saints are in disarray, and whilst Wuss are capable of having their day, they need a lot to go right for that to happen. LIrish need their opponent to have a bad day at the office to grab any wins.
So in short, I think there's 1 team standing alone at the top, and 1 team sitting alone at the bottom, with not much to choose between the other 10 beyond issues of balance across the squads, with coaching, team-ethic and game-plan making the differences in that pack.
ETA, and long may this competitiveness and unpredictability continue, I love it (albeit I'd prefer all teams to be consistently playing well whilst being unpredictable, but I'm not sure that's possible across so many teams and so many matches)