Weak pumps
Tiny tubing (on the first ones anyway, has since been updated to 3/8")
Crap blocks
Crap rads
I would try and get something second hand if I were you, while what I have got isn't amazing it costs a bit less than the Tt and will hopefully be a lot better.
£47 has got me:
Hydor 700l/h pump
Asetek res
8 ft 3/8" tubing
Apogee GT block
1 litre feser coolant
120.1 Black Ice Pro rad
Sunon 120x38mm fan (gonna use a nexus though)