[crack - and the can of worms open]
Ok, here's my take on the whole thing, which is sure to create another lengthy debate but here it goes.
Like any car, the Boxster has some weak points and some strong ones. Remember though, on the internet everything tends to be a 'big deal'. Specifically regarding your question, yes there have been some motors that have blown. Again, just like any other car. The rub here though is a 'new' crated motor from Porsche (w/o any assistance $$) will run ~ $13-20k. Not a pleasant thought, obviously. Once you're out of warranty, regardless of mileage, there doesn't appear to be much rhyme or reason as to who Porsche offers assistance to and who they don't. I suspect dealer and brand loyalty plays a very big part but who knows.
Now, no one knows the real incidence b/c, shockingly, Porsche ain't telling. Sometimes the failures happen to garage queens, other times to those driven daily or driven hard at the track. Some have north of 100k on the clock, others under 10k. There are some cars here and on other forums that have over 250k on the clock and have never had issues - other have had issues w/ two separate Boxsters. Go figure.
So, some people want you to believe the incidence rate can be as high as 20%. Surely if it were even 1/2 of that the USDOT, NHTSA, FTC, CPSC, AG, Ralph Nader, etc. would be ALL over PCNA & PAG. Say for instance how they are w/ Toyota these days for what so far is turning out to be driver error in the unintended acceleration reports / accidents.
What are the issues? Well, there are a few more common ones - d-chunk failure, porous block, slipped sleeves, RMS and of course the dreaded IMS. I leave you to do a search for definitions of each.
So, what can you do?
Aftermarket Warranty:
Well, if you think an aftermkt warranty is a good idea, feel free to get one. Personally, I do not and prefer to self-insure. If you want to go this route - DO TONS OF HOMEWORK as the majority of these companies quickly go out of biz or find every reason in the world to exclude your claim. Again, lots of research...
IMS retrofit: [bigger can of worms opening]
There is a company (on the forum here so I'm sure you'll come across) that makes a 'retrofit kit' which claims to be beefier and better than the OEM IMS. You can have one of these put in if you like, and some have. Otherwise this topic has been discussed ad nauseam but to my understanding this aftermkt new/improved/revised part does not have any long term/high mileage independent results verifying it's claims to be better than OEM. Again, research and make up you own mind.
Bottom line, stay on top of the maintenance - regular and preventative. I would recommend parting ways w/ the Porsche recommendations on oil changes in 2 parts. One being frequency - even though the sump is 9+ qts, treat it like most other cars and instead change it every 5,000-7,500 miles. Secondly, especially if you have any RMS weeping, switch to a heavier grade oil (and possibly as some others have - something other than Mobil1).
Otherwise, the best advice is: drive and enjoy your new car. And do it often. The Boxster is an awesome platform for both driving and for wrenching on. Get a Bentley manual for it so you can do a lot of maintenance yourself - it truly is one of the easiest platforms to work on.
FWIW - Here's are some very comprehensive / concise sites w/ tons of links and/or instructions for maintenance and mods on the Boxster:
Pedro's Garage - DIY Projects
Pedro's Garage - Technical Articles
Mike Focke's Boxster Page
Incidentally, both of these gentlemen frequent this forum often and are always willing to gladly help out other Porsche, and specifically Boxster, owners.
Again congrats and enjoy your car.
BLK-300 
Hybrid Mode
