I actually really like the monkeys. All of the first stages are just the most adorable things, and only Simipour of the second stages causes me hesitation. It's the dreadlocks. I just don't like the look of dreadlocks. Otherwise, the monkeys are all great. The grass pair is my favorite, though. Unfortunately, Tepig is my least favorite starter, so if I ever want to use Pansage I have to get lucky and catch one in Pinwheel Forest.
That said, I have used the fire and grass monkeys as long-term team members in Black and White. I used Pansear with Snivy in Black version and I used Pansage with Oshawott in White version. Come to think of it, I prefer to play through Unova with a team of - specifically - Oshawott, Pansage, and Scraggy as my unevolved Pokemon. Somehow, having those three as my early-game team core just feels comfortable. =P