Skaven pros -

They have access to vast arrays of troops/troop types, and can get them in vast quantities.

The leadership rules they come with over-ride what would be a fatal weakness and combined with the new re-roll of all leadership tests allowed by the BSB and the generals leadership in a 24" diameter bubble thay have the same Ld as dwarfs, ie impregnable.

They have excellent magic capacity and at least one game ending spell, which is now far easier to cast now in 8th irresistably.

The new initiative srikes first regardless of charge now makes even their weaker troops likely to inflict a credible ammount of damage on all but the most heavily armoured foes.

The Storm Banner can, for a tiny cost erradicate their greatest weakness - being squelched by template weapons and shot to death - yes it affects their own troops to, but this is generally less detrimental to them than it is against other armys such as DE, HE, WE, Dwarfs, Empire, OK of which (generally) most of their opponents will come from.

Cons -

Such a large quantity of troops on the table means the potential for being bottlenecked against terrain, the newer terrain rules have nearly removed this as a problem for skaven now.

The ability to be lose all their Ld bonuses by being flanked was a great problem, but in 8th the most common flanking units, fast cavalry have been hit by needing full ranks to break ranks. To give the fast cav enough ranks to both survive getting to the flanks and then (as ranks are counted after combat now) last long enough to be able to break the ranks is an option. This falls under analysis tho as with 2.5k or 3k skaven can build a battle line that stretches from table edge to table edge and presents no flanks to the enemy.

Overall I believe skaven have really been boosted a vast ammount in 8th, but regardless of numbers they will die in droves in HtH against any and all opponents, its just a case of will they fail their stubborn ld 10 re-rollable break tests over the course of the game?

The above is just my opinion of how they could be played etc, etc. I have yet to play skaven in 8th and the scenarios have not been factored in to the above post, but the potential is there for skaven to do very well in this new game we call warhammer.