a. There are a few issues with the OS.To me everything's workin' ok,but many others post some bugs for the latest version (1.50).Although,the previous version (1.45) is better for sure but you can't take the advantages of the new one.Everything else is workin' perfectly.You can load multisampled programs as keygroups,the effects are descent,the sequencer is solid and you can have plenty of ram (512 mb max.) and HD as a storage sollution (80gb HDs workin' perfectly).Editing samples has now many new features than the previous models.
b. I'm feelin' this,cause i was ready to sell my 2kxl something that finally didn't happen.Anyway,learning the mpc4000 is easy if you're a good mpc2000xl user,but there are some things that you must learn about the structure of the machine,because many new "terms" are introduced in this.
My opinion:Buy the 4000 and keep the xl (you can make crazy re-sampling tricks and to have them both synchronized it's the ultimate freedom)
