Diskless means lower electricity bill is not true because the only thing you're not going to put in a rig is the HDD alone. And HDD consumes very low power. For me, personally, diskless is not worth it unless you're planning to set many rig like TNC or Minesky shops. If a problem occurs to the mother unit, all the units become useless. P@tching of online games may have been a problem in the past because of how shi**y internet speed back then but we have high speed internet now and p@tching isn't a problem anymore. You may be saving some cost on buying less HDD but considering how cheap HDDs nowadays plus you're going to have to buy top of the line LAN equipments, I'd rather buy multiple cheap HDDs. You need to buy top of the line LAN equipment because if you have crappy LAN, the transfer of files from the mother unit to other units will be slow. There's a shop here near my place which has a diskless setup and has crappy LAN and players are complaining that loading of games are super slow and internet browsing is the only thing decent to do there. Now, you very rarely see that the shop is full even though they only have 9 or 10 units.
Edit : WTF! 0_0 the word p@tch is censored in this site? AHAHA!