The 500-s is much easier to get to grips with.
But I wouldn't touch a clone again.I got through two of them.
The tm9101 is 400% better, but is a little less stable.
Also depending what card you want to share, will depend on if you have to use NewCS.
I have not had any major problems with the hard drive (I put a decrepit 40gb in at first and worked) but is works better with a 5400rpm drive and it's IDE.
99% of Enigma1 plugins (dm500s etc) works with the TM9101.
I am no going to lie to you,if you want to fully use this box, then it takes a fair bit to learn.
If you just want to CS then if you have used a dreambox or similar before it's a doddle.
Have a look here:
_http://tm9100.wikidot.com/start
and click on tutorials & it will give you some more info.