I upgraded my version of Parallels to version 3 as soon it was released on Friday. The major draw card for me was 3D graphics support. I like to play the odd Windows game from time to time, so this is a major(ish) feature.
There are a slew of new features, including the ability to boot a Boot Camp partition within Parallels.
Install was fairly painless. I have a XP parallels image and a Vista boot camp drive. I tried both. I didn't notice any real world difference in my existing XP image to be honest. My Vista boot camp image loaded nicely within Parallels. It has to load some drivers to the OS first and requires a couple of reboots first, but it up and running within 10-15 minutes.
The Vista image running under Parallels had Aero turned off, and I couldn't get it running even with Direct3D support turned on. It run pretty sluggishly too. Quite a bit slower than native boot camp. This is understandable I guess but a little disappointing. I think it is down to memory issues with Vista (my version is Premium or Ultimate or wtf it's called) as much as anything else. My machine is a Macbook Pro @ 2.16Ghz and 2Gb Ram. The image had 1.5Gb ram allocated to it.
My advice would be unless you absolutely need it don't run Vista in Parallels.
XP runs as fast as native under Parallels, in fact, running in full screen it would be impossible to tell it wasn't running native, using real world / seat of pants benchmarking.
The marketing blurb on the website says, "New! 3D Graphics lets you run today’s most popular PC games on a Mac". This is a little misleading.
I downloaded a demo of Star Wars Lego II and it crashed on the menu screen. There is a list of games on the website, one of which is Quake 4. I downloaded the demo - I also downloaded the native Mac version, but haven't benchmarked yet.
Quake worked fine, but in game fps was hovering around 14-18 on average. I had medium detail turned on, with shadows but no AA, running @ 1082 x 768.
I will benchmark against native Mac version be commenting. I would have thought however that 14-18fps would be quite low however.
Overall, Parallels is great and I recommend it to anyone. Word on the street suggests that something similar may be built into Leopard. Time will tell on that front.
I would hold off on buying or upgrading, until after the WWDC which starts today (11/06/2007) as this info will become more clear then. Also, if you are looking to run the latest PC games, I still think dual booting with Boot Camp is the best way forward.