As much as I love the interface and idea (I really do) and I love the App, for me as an operator it requires making large exceptions in my connection limiting.
I usually only allow 25 connected users from a single IP, and I use GeoIP to get people a node near them- so- when people connect using irccloud they lose that benefit, and it means I have 100's of connections from ealing.irccloud.com-
in the past there has also been some issue with availability, it's weird when netsplit like events happen and you have no control. (although I believe they fixed the issue with ddos)
personally, I don't use irccloud day to day, I use xchat and 'Palaver' for iPhone, which my friend develops- he also maintains ZNC so his app has push notifications on highlight. (as long as you're not connected to ZNC or your client is marked 'Away')
Everything of his is open source (except palaver I think, it's paid), so; if you're interested in IRC I'd take a poke.
https://github.com/Palaver/znc-palaver
he also intends on making a web client, similar to irccloud, however he's terrible at design so don't hold your breath.