Rose is incredible, Citron is pants
After playing through the 10 hour trial I've got to say the Rose is incredible, the damage plus fast fire rate for long range coupled with abilities to render people useless at close range makes her the only plant worth playing. A team of Rose's can seriously dominate any game.
The Citron on the other hand is now just rubbish, his lack of damage plus fast burn out time on his cannon makes it extremely difficult to kill anything.
Other things of note, the base Cactus' primary fire seems odd. She was a great long range sniper but the fire delay makes it actually harder to hit things at long range and she has zero utility at close range. The base Cactus was my overall favourite character from the first GW.
From a Zombie perspective I actually think they are evenly matched. The Imp might be a little too weak however.