I have just gone through coming from scratch into trying both native Android and Phonegap. Phonegap can be a good idea if you want to do something on Android which does not require specific phone features not covered by phonegap (because otherwise you will be both working on phonegap and android native for developing phonegap plugins =D).
On the other hand, Android introduces a bit of complexity on the management of the Activity lifecycle which you do not need to worry when you use phonegap.
So, if you do not need a very complex application, but something that could pretty much work well as if it was a simple web application, or if all phone features you need are supported by phonegap, phonegap is perhaps the preferred choice (specially if you are already familiar with web development).
Ah, and off course, you cant expect a phonegap application to have the same performance as a native one. But again, if your performance requirements are not too high, it is perhaps worth considering phonegap.