Been sort off and on watching A1GP, it is exciting sometimes, but it really isn't fun to watch after a while I think.
There are only 3 or 4 top teams that they focus on the most, and even then, they aren't the 'best' drivers I think. A1GP kind of takes some lesser known drivers under its wing, and it is neat to see some of those drivers... it just isn't all that great to watch with some of the track choices they have I think.
For me, Champ Cars and F1 are the main motorsports worth watching if you like open wheelers. F1 isn't all that dull, how is it dull? It is surely interesting to watch this new season unfold, and F1 has always been exciting at the starts and finishes... but never in between. A1GP is no different though, there is hardly many good battles at the finish, and it just gets boring to watch. Happens in a lot of racing series even.
I ignore that fact as much as I can though, and I can really only rate a series being 'exciting' if it has aggressive driving, fast drivers, and some accidents. You don't find a huge amount of that in open wheel racing because it is so dangerous (versus sedans for example). I'd watch BTCC, V8's, or WTTC if I wanted to see some good door-to-door action. F1 is just the 'sex appeal' for us guys, and the cars (and drivers) are amazing to watch, that's all I can argue for F1 being better.
A1GP is really a 'behind-the-curtains' sort of series, they aren't really spreading the word, and it is really hardly acknowledged as a true race of nations by most motorsports fans. Personally, I see it kind of dying off with how much that series lacks. Unfortunately... because I'd like to see it grow into a bigger spectacle.