I have used my 205 at the track for dialing in the pace I wanted to run.  When I run the indoor track I turn the GPS off and use it as a stop watch and lap counter.

I'm also loving my Garmin now too. I used to use RunKeeper. I love looking back at my splits. I can't wait to use it in a race.

When I first started running intervals, I'd take a notepad and a pen to the track.  I'd hit my $10 K-Mart watch every interval and remember it for 3-4 intervals and then write down the times.  Then, I got a Timex Ironman and have used that for the last four years or so.  I love the Ironman but I have grown very tired of running the same routes over and over and over and over and over.  Now, I can decide to run for an hour, run wherever the hell I feel like running, and not have to remember every turn I took.  Good stuff.

I have also found it interesting to see how slow my first mile is in comparison to the rest of my run.  That's not a bad thing at all as it tells me I'm starting easy and that's goodness.  Last, and perhaps most importantly, there are times I can't use the track for various reasons.  It will be cool to be able to do intervals even when the track is unavailable.  I've done them before on time rather than distance but staring at your watch is a pain in the ass and you really don't know your exact pace that way.

I'm using the Runmeter app on my iPhone. What are the advantages of a GPS watch over GPS apps like Runmeter?

Way more accuracy.  Plus other nifty little features if you choose to use them.