PhD, Startup, or Career? 
physcab: Well first, be thankful that you have incredible options.  To be fully funded for a PhD is not unusual, especially for engineering/science fields, but in this economic climate there are far more people applying for fewer positions. The same goes for the job offers.That being said, what do you really want to do? What are you good at?I've written a bit about PhD life in another post (http://news.ycombinator.com/item?id=445082) and of course you are welcome to contact me if you are being pulled this way.  Bottom line is that I think you should do the PhD if you are completely ready. Putting off a PhD will only make coming back to do it much more difficult, especially when bills start to pile on.  Getting a PhD is not setting your life in stone, rather it will open up MANY MORE doors for you in the future.The start-up sounds enticing. If you two agree about how much work needs to be done and this is an area that you are truly passionate about...just go for it!  However, know that good ideas are not finite.  There will always be time.As for the job offers...  Well, I tend to hate the corporate environment so I couldn't give you unbiased feedback. If you feel you can create value, and feel like your skills are valued, then perhaps its a good match.With any of these, I would encourage you to talk with the people you would be working with.  Your community will make a HUGE difference POST-college, because life after undergrad is shockingly different.