There is no problem with a phase one or two...just go for the lowest miles u can find with ffsh
The only differences are and extra lambda sensor, a different way of setting the valve clearances and a revised end bearing on the crankshaft with slightly more float.

Common faults;

rusty sills, panel join under rear lights
heater controll valve fucked
rear beam bushes
arb bushes
steering wheel melting
Some people complainf of 'blowing them up' when in fact poor servicing or lack of checking the fluids regularly is to blame. Some had problems with oil usage because the oil control rings could fail, u'd notice this through smokey running and obviously a low oil level! I have head of a few peeps having leaky valve stem seals too but again this isnt widespread.

Also dont listen to internet bullshit, it's a very very tunable engine and has been announced by caterham in their latest lineup. See www.shawspeed.com for tuning ideas