I attended in 2010, Friday-Sunday. I've also been to Laguna every year since 2006. Indy was a letdown as far as the venue was concerned. The folks were nice, parking was easy, and there were not many hassles, this is all true -- efficiently run all the way around. But no buzz. Even though there were 20-30,000 fans there on Friday and Saturday, and I believe they had 45-50,000 attend the race on Sunday, the place is so cavernous that it felt empty. Even the bikes don't seem that menacing and loud in such a huge space. Part and parcel of being such a large place, it is not possible to walk the track and see any practice session from more than one or two vantage points. You more or less have to pick one spot for each session and stay there. Contrast to Laguna, where in the space of a single 1-hour practice session you can start at Turn 1, then walk the track to Turns 3 and 4, go up the hill to the corkscrew, and then double back to Turn 5 or head down Rainey curve to Turns 10 and 11. Also, at Indy the paddock area was also very low on excitement, vendors, memorabilia. Good news, the beer lines were very short.
Downtown Indy also lacks buzz. To be sure they do a nice job closing down the main drag and getting a party going, but it is pretty small scale. The upside to my Saturday night at Indy was literally bumping into Dani Pedrosa (and you guessed it he was trailed closely by Puig). He looked to be out for a stroll the night before the race. Tellingly, I was the only one who recognized him. I wished good luck and patted him on the shoulder.
I can't really comment on the track itself, but can't think of any MotoGP riders who would miss the track from a riding standpoint. No one really jumps up and says the track is great.
So all in all, I would prefer going to the Indy race versus not going to any race at all. But it was a letdown.