In my opinion, Club World is one of the most reputable RTG casinos online, and RTG slots are also enjoyable when they are in the mood to pay, lol.
There are only two basic drawbacks to these slots in my opinion:
1) The random jackpot has the effect of lowering the RTP percentage slightly, i.e., the casino uses a portion of your bet to contribute toward each slot's random jackpot. Personally, I'd prefer to play a non-random jackpot slot that pays better in the base game, but they don't offer that.
2) There is a max win rule in place on almost all their slots - I think it's something like 50,000 your line bet. So for purposes of illustration, if you were betting $0.25 (25 cents) on a slot, the most you could win on any one spin is $500, and for slots where the paytable shows you should have won more than $500, your balance simply stops growing for that spin. (Free spins and/or bonus rounds count, for this purpose, as a single spin. So even if you get the 100 free spins - for example - on Rain Dance, you can only win 50,000 line bet from these spins altogether, max.) Vulcan is an exception to this rule in that the max win on this slot is 150,000x line bet. For most players, they won't encounter this limitation; of course, when you DO, it sucks that you didn't win more.
Hope this helps.