Im on my first Citroen Cx, but not my first Citroen. I also have Xms and a xantia.
The Cx is something completely different, yes it has hydraulic suspension but it has a very different feel to your standard hydraulic citroen. If you have not yet experienced a "magic carpet ride" then you should, and what better car to try it in than the cx
Mine is a series 2, 2.5td (Turbo 1) in white.
Turbo 1 just means it doesnt have an intercooler like the turbo 2 so is a little bit slower.
It is a great car to drive (just wait untill you go round a roundabout though), and maintenance is not as bad as people think!
As with any car of this age it is body rot that will kill it not the mechanicals.
If its got a sunroof then be a bit wary as these tend to rot massively, the other usual rot spots tend to be anywhere that metal has been used!
If you can get one without the metric tyres you will save yourself a headache too as these tyres are rather expensive!
If you can afford to pay a bit more for a better condition one then thats the way to go.
The series one cars have a more classic look to them, but I believe a well looked after series 2 can look modern and pretty damn good.