I love the XA. While agreeing with Jay as far as <60k projects go, once you must go beyond nothin' could be finer. Everything George says about his favorite is true for the XA as well and compared to the stupid Intel 251, the XA is a MIPS demon. There is a previous posting here with access to the XA freeware (assembler, simulator, '51 code converter). The Ceibo EB-XA (a 95% as complete as the $many ICE jobe) is available from Philips for about $400. The flash XA versions require software (free) only to program, you can put your EPROM burner away. However much I love the XA, I would never suggest it as the right solution for everything. You state that you are a hobbyist, that, of course, may make you use it for everything.
Happy new year
Erik Malund