Well I used Xilinx for Spartan-3 and honestly I had a lot of difficulty getting on with xilinx tools… to be more precise,, their documentation/user manuals suck in a way there is lot of textual description..but no pictorial explanation of how to use them…
now I have been using Altera Quartus for like 8 months and I’m perfectly happy with that…
Altera Quartus indeed is easy, clear to understand and its like whole flow of tools linked with each other..
so if you are designing your FPGA , you do get what are you making while using quartus…
my favorite tool in Quartus is ”Block design” and ” altera PLL’s” ..they just make it simple for me ….
seriously , if you now look over internet, Altera’s marketing is awesome ..I do see that Terasic technologies is doing wonderful job in making altera’s product user-friendly. =)