I've been using iPhoto lately, and I've been using it a lot.
First to the RAW issue. Does Apple make use of RAW? Yes and no. When at first you load the RAW, the changes you make will use the RAW file as source and apply them, not wasting your precious data. However, it will save the changed file as a JPEG. Thus, next time you make a change, iPhoto will NOT use your RAW file, apply the changes you did before and the ones you have made now and save that as a file, but it will use your intermediate JPEG file, thus wasting more information than necessary. This is most apparent when you use external programs. Try dragging your fresh file to an application, and it will be served a RAW file. Make some changes in iPhoto, and it will be served a JPEG. Can this be solved? Yes, it's quite easy for Apple to save a trail of what modifications have been done to the image as metadata to the image and apply these when making changes later. It will take a bit longer to save the file, but that will defintely be worth it.
Second, not being able to select a whitepoint is a hassle. For the pictures you're not passionate about, this is not a problem, but to the ones you want to give your best attention, iPhoto will not be what you're using. Selecting a whitepoint is so quickly done in other programs
But iPhoto 5 is WAY faster than iPhoto 2. I've been hitting it with my 30mb/photo negative scans (the Nikon Super coolscan 4000ED is doing a great job backing up my fathers negatives), rotating and cropping away. I've been touring Denmark with this years Very Big Band project, taking 4gb worth of photos with my Canon EOS 20D, organizing the lot and putting it together with iDVD. (The iPhoto/iDVD combination does not work super as there is no other way than manual to change the sort order of the iPhoto pictures when importing them to in iDVD. And once it's cached a iPhoto folder, resorting the folder in iPhoto won't help either) Sorting, rotating, simple editing and organizing the photos and burning them to a DVD (iPhoto format) is easy, if you don't mind waiting 5 seconds now, 10 seconds after the next edit and 5 seconds to create a folder.
Bugs? Yes sir, the progress window will keep open forever when I've been editing files, and the program will often go into what looks like an endless while when it's not used, leaving "force quit" as the only option. Doing too many things at once seems to confuse the editor and make it do only a few of the changes that were asked for.
So is it worth the upgrade? For me I'd say a definitive yes. I'm more organized with my photos as iPhoto 5 can handle more pictures quicker than iPhoto 2 could. Is there room for improvement? Yes, very much. Hope Apple will release upgrades beyond the 5.01 upgrade, which I believe they did not for iPhoto 4.