Hey Lefteye. I guess that depends on what sort of work you are doing. Nearly all users of the XL1 I have known never used anything but the stock lens. It just costs so much for extra lenses that many people don't bother getting them unless a situation specifically demands it. Since the 20x lens on the XL2 has such a huge range of focal lengths getting another lens on top of that isn't really necessary. If you do get a lens for shooting film style stuff I recommend the 16x manual lens. The normal 20x and 16x lenses use servo controlled rings for focus and zoom. This isn't a huge problem but it can be annoying if you want to repeatedly change focus from one point to another or when you need to make _very_ slow changes (slow changes do not register because the lens is set to ignore small changes from accidental bumping etc. A slow change is seen as many small changes and completely ignored). Unless you plan on spending another 1K and up I would evaluate the XL2 with only a single lens (as if it were fixed) because very few people change the lens. It's certainly not a necessity for most people. If you want to do documentary work or event recording the XL2 has a huge advantage over the DVX. The 20x lens has much more reach than the 12x on the DVX.
The DVX, indeed, does not have true 16:9. Whether this is a problem or not really depends on your output medium. On DVD the difference will not be large at all. Going to film the difference will be very visible. The DVX looks good on the bigscreen even when cropped from all accounts so the XL2 can only look better in this regard. I personally own the DVX and don't mind using letterbox or squeeze mode. I would, of course, prefer true 16:9 but the cameras other features make it the better choice for me.
As for color rendition: I suppose that depends on what you mean by color reproduction. Both cameras are pretty much on par in terms of reproducing a scene with true color. What people are probably refering to is the cinegamma modes on the DVX. Many people find the cinegamma controls on the DVX to be superior to the XL2 cinegamma. I personally find this to be accurate but it's really a personal preference thing. The DVX, in cinegamma mode, _does_ hold color in the highlights and shadows better than the XL2 though. This is part of what people are seeing I believe. It's not a drastic thing but it can be noticable.
Honestly, if I were going to spend that much money on a camera, and I could wait, I would wait until the HVX200 comes out. It will be only marginally more expensive than the XL2 and it will allow you to shoot DV like the DVX onto DV tape while also allowing you to move up to HD and DVCpro50 when you are ready and can afford the P2 media/hard disk solutions. It too has true 16:9.
Really, you can't go too wrong with either of these cameras though. Both are great. Really it comes down to whether you NEED the features of one camera more than the other.