The one time I tried to make a warranty claim for an annoying noise from the roof on my E93 was a bit of a disaster as I got messed about by the dealer and I had to end up paying for the repair as it turned out it wasn't covered under warranty, even though the service manager said it would be. However this might have more to do with the ineptness of the dealer than the actual warranty.
I have heard very positive things re the warranty otherwise and with the "well known" issues on the 335i engine, I don't think I'd want to run without one so I will be renewing mine in a few months on the monthly scheme which is quite reasonable. The only downside is that you are locked into main dealer servicing.
As for the emergency assist, the one time I have had to call them out for a flat on one of my RFT's, they were brilliant. Arrived in about 20 minutes and transported me, the OH and a friend home on a dedicated low loader and offered to take me to a garage the next day if required so well worth the money I reckon.