I don't think there is a definitive answer, it depends upon your need. Personally I think Citrix is oversold in schools, one head sees another school uses citrix, therefore the buy into it too. We use Citrix and it suits us (300 odd clients and 8 servers) but I've seen other schools who have had a look around here and paid a lot of cash to do the same, but only for 30 remote desktop machines! totally pointless.
I know that it is something that is interesting to me and something that I'd possibly like to look at. So the kind of thing that would be useful to know is what part the Citrix presentation server plays, what you get to provide desktop environments and stuff to do with licensing.