Yes its been discussed thousands of times, and you'll find no definitive answer i'm afraid (make sure you expand the date range in the search page to more than the default 30 days setting). Internet forums always bring out the disasters and rarely praise the cars, even this one !!.
RMS - if its one drip a week then concensus seems to be not to worry too much and leave it til it gets worse or the clutch is due a change. If its just sweating then don't bother. The revised seal and installation procedure is improving matters, but isn't necessarily foolproof. I've had no issues with my old 2004 2.7 or my current 2006 3.2S.
ISF - it can affect any car up to MY06 when the bearing size was increased in an attempt to reduce the failure rate (not aware of any failing with the improved design). Failures can happen at any time, but a high proprtion of the failures seem to occur around 30k +/- 5k miles. If a car has reached 50-60k miles then you can probably be a little more confident !. Its all about your exposure to risk, but there are cheaper alternatives to the Porsche warranty, such as the premier one from Tesco at around £420/year. or a slightler lesser one from Tesco for around £330/year. These will give full or significant coverage for IMS failure and engine replacement/rebuild/exchange. Porsche will ask £11k for an engine replacement out of warranty, may offer soem goodwill. Independents such as Autofarm would get the cost of a rebuild down to £7k or maybe less.
How often ?? - if you join enough forums you will hear of a failure every 2-3 months on average. The good news is that earlier cars will have more miles on and are maybe ???? less liable to future failure (if they were going to go they would have gone by now attitude ).
Just remember you are buying what was and still is a £40-50k sportcar, you will not have Ford Focus running costs, and you need to think about warranties or holding back some funds for contingency.
