These days, the line separating a smartphone from a tablet seems blurry. For instance, the Samsung GALAXY Note has a 5.3” WXGA (1280 x 800) screen. The Pantech Vega R3 has a 5.3" display as well. There are rumors of a Google Nexus 5. Plus, I can't help but wonder if Dell will revive the Streak 5 (probably not, but you can't help but wonder...)
The upcoming Samsung GALAXY Note 2 will have a 5.55" HD display.
The small tablets like the Kindle Fire or the Nexus 7 have 7" screens, so these 5" phone/tablet or "phablet" crossover devices can be viewed as either being a really large smartphone or a small tablet. Plus, these larger smartphones often come with built-in stylus pens like the Samsung S Pen stylus.
For me, the perfect combination seems to be a regular smartphone and a 7" tablet. For a while, I was using an Android smartphone + iPad. These days, I'm doing the iPhone + Android tablet (although I've temporarily gone back to an Android smartphone because I'm recycling my iPhone 4S and waiting for the iPhone 5).