Snover certainly isn't a bad option, but isn't a Pokemon that I'd personally use. Snover and its evolution Abomasnow certainly have their merits though, in particular their very early access to Wood Hammer, a great Grass-type nuke that will deal very heavy damage to anything doesn't resist it. If Wood Hammer at level 36 wasn't enough, Snover also gets Blizzard at level 41. If you'd like to get access to Blizzard faster, cancel Snover's level 40 evolution and take it to level 41 first when it learns Blizzard (Abomasnow gets it later at level 47). Alternatively, you can get it via TM.
Blizzard is an especially good option on the Snover line due to Snow Warning, which gives Blizzard 100% accuracy, making it a powerful and reliable Ice-type move. The Snover line's great STAB attacks make up for their fairly ordinary offensive stats. As mentioned, Snover evolves at level 40, which isn't too long after you first encounter it at around level 33 at Route 216. Snover comes with a decent priority move in Ice Shard when you first encounter it, which can help it pick off weak opponents. Snow Warning as an ability is useful outside of Blizzard too; it will deal chip damage to your opponents, but won't damage Snover, as it is an Ice-type Pokemon. Abomasnow has a really interesting movepool including three HM moves, Earthquake, Rock Slide and Brick Break among other things, which you might find useful to teach it.
Though the Snover line is definitely useful, it has some very noticeable flaws. These put me off wanting to use it, but you can judge for yourself if Snover is still worth it.
- Snover and Abomasnow have a very unfortunate defensive typing that leaves them with a seven weaknesses, meaning you'll be switching them out of battle quite often. Their typing fares a bit better offensively, but is still walled completely by Fire and Steel-type Pokemon.
- Snover and Abomasnow are both painfully slow, which makes their weaknesses even more of an issue since they'll probably have to take an attack before they use one themselves.
- Snow Warning, as good as it is, doesn't do your other Pokemon any good, and will damage them turn by turn like it will to your opponents. Weather lasts forever in Gen 4, so unless you carry another weather-inducing move or Pokemon, you're going to deal with those effects for the entire battle. Additionally, Snow Warning's animation can get annoying to watch every turn, keeping in mind D/P's slow battle animations.
- You have access to Sneasel at the same times in the game, which is a fantastic option for in-game playthroughs due high Speed and offensive states. If you're in need of an Ice Pokemon, Sneasel might be a better Pokemon to train.
- Snover and Abomasnow have a slow growth rate, which could make training them a lengthier process. (This means they require more EXP to level up.)
Due to their low Speed stats and weaknesses and for being outclassed in part by Weavile, I'm personally not a fan of the Snover line. As stated before, though, they're certainly not bad options, and don't match too badly in upcoming fights either. They resist STAB attacks from Candice and Volkner's Pokemon and will do great Bertha's Ground-type Pokemon. Aaron, though using Bug Pokemon, uses two Pokemon that are part Flying type and thus weak to Blizzard. Abomasnow has nothing against Flint, though. Cynthia has three Pokemon weak to Ice and one more weak to Grass, so Abomasnow might be useful in taking her down. Her Garchomp's double weakness to Ice could make Abomasnow a great Pokemon to use against her strongest team member.