A few improvements I've down that makes life easier and makes a big difference to the care and feeding of your Felix printer:
1) make the Extruder fan 12V instead of the default is 5V there is jumper on main board to solder from memory. this provides more cooling to the extruders and prevents hot end jams on retraction.
2) Insulate your hotbed with a piece of cardboard underneath, will protect the Y-Axis mounts from heated bed, but also allow you to go past 80Degc if you want to print ABS, which is my filament of choice nowadays, I now get upto to 105DegC in a chilly office.
3) Replace the Z Axis Stop with this one found on the forums, so very much better
http://forum.felixprinters.com/viewtopic.php?f=9&t=890 and is a real breeze to adjust
4) Replace the levelling spring washers on the hotbed with springs from IKEA Pegs
5) Replace the Setscrews used on the Hotbed levelling with 3mm Cap Screws of roughly the same length, much easier to adjust using an allen key rather than trying to adjust the nut with a spanner, just have to be careful that you don't over tighten into the build plate. Now I can adjust on the fly while printing with a single allen key.
6) Use 3mm glass plate on the build plate.
7) if every your belts need replacing, replace with GT2 Belts, felix originally comes with M3 belts, which are hard to source and cost a bucket in freight getting them from the Felix Store, GT2 is easy can be found anywhere and the bonus is that they increase the X and Y step resolution using. You also need to replace the drive pulleys.
8) I put connectors on all my X-Axis Extruders hot ends, Fans, Thermistors and Stepper motors. Makes it easier to dismantle and remove for cleaning or maintenance. Same goes for the hotbed, but some high amp connectors to make it easy to disconnect if every you need to remove the hotbed.