This review is written from the point of view of someone using this camera for making independent low-budget films. I will cover negatives, mitigating factors for those negatives, and finally discuss the reasons you should buy the camera.
Let's get the negatives out of the way first: the R60 is not a "prosumer" or professional camcorder. It lacks many of the controls and jacks that you'd want on a high-end camera and it requires some cleverness on the part of the operator to work around the "full auto" behavior it wants to have. You don't get a hotshoe, XLR, SDI, or any external manual controls for the imaging hardware such as the focus and iris. It takes MPEG-4 AVC video in 4:2:0 color space which can cause some halos when chroma keying (AKA "green screening") in post-production. The included battery doesn't last as long as you'd probably like, especially if you plan to spend many hours shooting footage. Low-light response is grainy because the sensor isn't made for it. Being so light means that camera shake can be a problem, even with a steady hand and the built-in image stabilization.
You need to understand these limitations to make the most of the camera. Now, let's talk about why most of those negatives don't matter much!
There is a 1/8" microphone input, so you CAN attach external microphones, but you need to be aware that external audio sources MUST BE SELF-POWERED. Fortunately, there are plenty of powered external mics and ways to connect unpowered ones up. The camera's manual controls are behind a few touches to the flip-out touchscreen which makes them impossible to change during a shot, but most of the camera's automatic functions track changes very well; about the only thing that needs to strictly be under manual control is the white balance and this camera does fine balancing against a typical grey card.
Cold shoe adapters are very cheaply available for attaching external on-camera lighting and shotgun mics. Batteries from Canon are ridiculously expensive for a camera this cheap but if you look for a "decoded Canon R60 battery" you will find fully compatible extended life third-party alternatives that are quite affordable and will give you about 110 minutes of shoot time per battery. In a pinch, this camera can be powered from its AC adapter!
Low-light response gets quite grainy, but the amount of grain is acceptable in many instances. If you're shooting a film you should be lighting your scene anyway. As for the chroma keying halo problem, that's what happens when you use a sub-$1000 camera; the 4:2:2 color space of more "pro" camcorders is preferable, but the truth is that 4:2:0 is not nearly as big of an issue with this camera because it shoots in 1080p. Halo artifacts are much harder to see at such high resolutions, and if you find that this camera's chroma keying performance for your shots don't quite work for you, resize to 720p first and the halos will almost completely go away.
For the camera shake problem you will need to get a weighted camera stabilizer. The best option for someone on a budget would be to build the "$14 Camera Stabilizer" by Johnny Chung Lee. Professional stabilizer grips exist but they start around $140 which makes them quite expensive for the low- to no-budget filmmaker.
There are plenty of positive reasons to choose this camera, too. One is the 8GB of internal memory. If you run out of SD cards on a shoot or one of your cards stops working or is damaged, you'll be VERY happy to have that internal memory available to fall back on. The stereo internal microphones on the front do a great job of recording environmental sounds despite the obvious issues with any on-camera microphone; you'll want to manually force the audio levels down because the default captures as much environmental noise as possible and you don't want that. The camera can shoot AVCHD or MP4 format video, but you should probably avoid AVCHD since all of the best shooting modes are only available in MP4 mode and AVCHD on this camera has absolutely zero quality benefits. MP4 can also be directly uploaded to YouTube and similar video hosting sites without modification or transcoding involved. You can choose from 1080p in 24p, 30p, or 60p frame rates; there is also a 4Mbps option that records 720p in 24p or 30p frame rates. There's also the worst-case scenario with cameras: breakage. If you bust a camera like this and are out $400, you're a lot better off than if you busted a $1600 prosumer camera!
If you've heard about how DSLR cameras are all the rage for filmmaking nowadays, I can tell you from personal experience that they are not as great as they're hyped to be and the limitations are extremely frustrating and expensive to work around. The R60 produces better video than all but the most expensive DSLR systems when you add any sort of movement at all. DSLR systems don't have silent auto-focus, automatic exposure control, and require very expensive camera rigs to even be able to function like a camcorder. MPEG-4 compression on DSLRs is usually in 4:2:0 color space just like the R60 and often has worse compression, plus DSLRs can overheat and can't usually shoot more than about 20 minutes of continuous video. Considering an R60 costs 1/6 the price of just a single 5D Mark III DSLR camera body (that's no lenses and no camcorder rig at all) there is simply no comparison. Your cheaper DSLR may take better "still video" and is good as a second camera, but the R60 will always be a better choice for filmmaking than any remotely affordable DSLR.
If you understand the limitations and how to work around them, this camera is an excellent camera for filmmaking. The price is amazing for what you get and the quality of the video is spectacular. I highly recommend it.