Positives of Suspects missing:
1) Lead pokemon have varied greatly. The five most common UU leads in May were Crobat, Uxie, Ambipom, Rosearde, and Yanmega. With the removal of Crobat I've seen a lot more Arcanine, Moltres, and Omastar leads. Furthermore, more than 1 out of every 10 teams used Crobat as a lead in May. From my recent experience, I would say Ambipom has been the most common, yet it has not come close to 10%.
2) Physical wall choices have become more varied. What used to be purely Regirock, Registeel, and Steelix has evolved to include Slowbro, Claydol, and Weezing much more often.
3) Pokemon requiring set-up have become more common. Curse, Calm Mind, Sub-seed all seem to be returning as 130 base speed taunt is gone. Shaymin's dismissal allows Sub-seed to prosper and removes one of the largest offensive threats to setting up.
4) Fighting type pokemon are more prevalent. Due to Crobat's 4X resist to fighting moves, Fighting types were at a severe disadvantage. Prior to Crobat's dismissal you saw Foresight Hitmontop and few other fighting types. Without crobat, the other hitmons, hariyama, and Toxicroak appear to be far more common.
Negatives of Suspects missing:
1) Pure offense and Sweepers lack as many checks. Swellow with Quick Attack, Absol with Sucker Punch, and the various Choice Scarfers available do a decent job of taking care of runaway Blazikens. However, Espeon, Mismagius and Spiritomb are running wild as they have the ability to calm mind more effectively. Curse Umbreon lacks anything that can threaten it effectively. Nasty Plot/Swords Dance pokemon, such as Houndoom and Drapion, have less to worry about as they can outspeed the fast majority of the metagame.
2) Stall teams lack a way to deal with wall breakers. Blaziken and Nidoking are much more effective than previously as they lack Crobat's threatening presence. Furthermore, neither needs to carry a Choice Scarf anymore, which greatly increases their effectiveness.
3) Weather Teams are becoming too prevalent. Shaymin and Crobat combined as an effective check to Rain teams, while Crobat and Honchkrow took care of Sun teams. Since their dismissal, almost 20% of the teams I've seen have been either Rain or Sun based.
- Most of the Pros and Cons are only effects of Shaymin or Crobat missing. Honchkrow's dismissal has done little other than exchange Honchkrow for Absol. However, it has removed a major problem for Sun teams.