Great selection, Prices not so great.
180G Pressings are all the rage now, so if you're into that whole "schtick", this is the place for you. I can't justify paying $70 for Nirvana's "In Utero", or even $35 for Depeche Mode's "Violator". It's the whole CD pricing ~thing~ all over again.
You can find some reasonably priced good stuff here, but I'd treat Sonic Boom as a very last, last, last resort if you're desperate for what's not in wide circulation at other shops (ie. The Cramps, The Cure, New Order, Joy Division, The Smiths, Morrissey).