I have ordered from reefcleaners and reefs2go several times, the stuff you get is micro size, so to me their packs labeled as "100G CUC" is really only suitable for 50G tops. I gave up trying after spending hundreds of dollars with online CUCs. I would rather spend $15 for 5 crabs or snails from my LFS because they are giants in comparison to what I have received online, and the 5 items from my LFS out compete 50 of the same item from online places (ie. 5 large snails do much more cleaning than 50 microscopic snails). Last time I dumped $120 worth of snails, crabs, and shrimp (12 peppermints, not 1 touch aiptasia) from reefcleaners into my 60G, all the snails sit at the top of the glass/tank in the corner, 6 months later and never seem to move or cleaned anything. The amount they say they will send is good, and they arrive alive and are active after a 3 hours drip acclicmation, so nothing wrong in that respect, just the micro size specimens is my biggest gripe with online vendors of CUCs.
Fish.. there are good places, but not cheap. Shipping is the killer on top of the cost of the fish, which in my area online prices are 2-3x more expensive for the same fish, but you do get a 14 day guarantee from LiveAquaria, 7 day from Blue Zoo which somewhat justifies the extra cost. If it is a rare fish you really want and your LFS can't get it, then online is your only option. LiveAquaria and Blue Zoo Aquatics are IMO the top 2 places to order fish from online.