Blastoise SW is our buddy Blastoise Base reincarnated with a few more side-effects. 120 HP is solid for a Stage 20, +30 Weakness to Lightning is ok considering Electivire isn't as played as much, and a Retreat Cost of 2 is average. Its Poke-Power, Waterlog, is nearly the same as Base Blastoise's Rain Dance, but now you have to give up attacking the turn you use it, which could hamper you. Hydro Pump does a mere 50 for 3 energy, but can be boosted to up to 90 for 5 energy; in other words, avoid using him as your primary attacker.
Modified - 8/10 (I'm surprised more Water decks aren't showing up and using Blastoise, but then again Blastoise lacks a real solid partner at the moment)
Limited - 9/10 (If you can get this out and you have a bunch of Water energy in your hand, you're in good shape)
Unlimited - 1/10 (Base Blastoise anyone?)