[celever]

I did use a Maractus actually... so I suppose I will do the write-up since I'm probably the only person who has. So:
Maractus -- Mid tier
Availability: Well its in the desert at a pretty low encounter rate (10%) so it won't require loads of searching. Besides, at that point you are probably under-leveled for Elesa so while you search you can get in some training. Also you can either have this thing, Sunflora or snivy at this point for a grass type and I would go Maractus for sure out of the 3.
Stats: It can be used as a very nice mixed attacker, however its speed kind of lets it down. It is basically a slightly worse in terms of raw power, but slightly faster specially oriented cacturne in relation to its stats. However Cacturne isn't in this game, so your stuck using this if you want a mixed grass type.
Typing: Grass... now this is good and bad for Maractus. On one side it is between this thing, Sunflora, Snivy, Lilligant (very rare though) and leavanny at the point you can get Maractus. On the other side Grass is not a great typing in B2 and W2, facing type advantages against Marlon and Clay only, but if you want a grass then this is generally what you are looking for, especially if you wanted one of the other 2 starters.
Movepool: This is where it starts going down-hill, and up-hill at the same time. Maractus is blessed with 4 pretty nice types in flying, grass, dark and bug. Unfortunately the only bug move it gets is pin missile, which is too weak to be useful where bug is in this game. To remedy this is sucker punch, giving it some semi-reliable damage on the elite four. Then is aerial ace, which is a pretty nice move for Maractus too, however you only obtain it after Skyla, if you really want a flying attack before then though there is peck via move relearner in driftveil. The good thing though, is that taking something like Lilligant which has technically better stats, Maractus can use sucker punch and other things to set it apart from lilligant's grass/normal/hidden power coverage.
Matchups As mentioned before, it is not great on the majority of the league in terms of STAB. It can however, use sucker punch and aerial ace to really hurt some other gym leaders and, namely, the elite four. Also as long as grass is not resisted it can really deal loads of damage with a needle arm or petal dance. Marlon is also laughably easy with this thing.
Additional comments The virtues of being the main good grass type in the game that is not the starters, a pretty nice movepool and even an immunity for an ability I think places Maractus firmly in mid.

I'd love to hear comments though, as always. (Did this in a bit of a rush btw)