I was wondering if I should edit in after effects and just skip premier all together. Does anyone do this? What are the pros/cons?

I'm sure there are pros, but I can't think of any at the moment.
Cons: AE is not an NLE, it doesn't work well with audio, and the export formats are limited.

Even when I build up a 30 second motion graphics clip entirely in AE, I take it into PPro to add audio and export it.

I concur ;)

Even though I love AE, it just isn't made to edit video like Premiere. However, for 30s spots, I tend to do everything in AE and either Dynamic Link into Premiere or just export uncompressed from AE and import into Premiere. And for openings, I do everything in AE and then use Premiere to add audio.

With Dynamic Link, there are many ways to integrate Premiere and AE. For example, you can do a basic edit with no effects and transitions in PPro and import into AE for effects, transitions and grading aka finishing. Another option is to edit in PPro and dynamic link each cut into AE for effects and grading; however, I have found slight issues with transitions and effects within Premiere.

For animation, text and grading, AE is a very very powerful tool. I have been learning DaVinci Resolve on Mac and I have been able to apply those lessons within AE for great color grading, albeit much slower than Resolve.

I've always leaned more toward AE for my work and after going CS5, even more so. I work in AE, export to PP for export of final work with audio laid to it. I now do all me color grading in AE and have pretty much given up on PP for it.

Thanks for the feedback all. Steve, I do the second option you mentioned and I think I should probably experiment with doing the first option. What brought it up was Stu's video:
DV Rebel Tools Free for After Effects CS5 on Vimeo