Hi Joe. I use a Dexcom SevenPLUS CGM, and I'll try to answer your questions to the best of my ability.
1. This will depend on where you wear the sensor, and how your body responds to the adhesive. Although the FDA has only approved the stomach for sensor placement (and thus, Dexcom and Medtronic will tell you that these are the only places you can wear them), there are many other sites you can use, which may be less "in the way" for you. For example, you can use your lower back, outer thighs, and arms. Typically, the adhesive will start to pull away after several days, but there are many products out in the market which can help remedy this situation.
2. Not really. Of course, this is coming from someone who already wears an insulin pump, and is pretty used to the feeling of "wearing that thing" all the time. It feels weird each time I put in a new sensor - like I'm afraid I'm going to bump it into something, or twist the wrong way. But, after a few hours, I generally do forget I'm wearing it. The Dexcom sensor lays pretty flat to the body, so it hides well under most clothing, as well. Of course, there is a remote (they call it a Receiver) that you would need to carry around with you, to read your results - but this can be stashed in a pocket, or clipped onto a belt like a cell phone.
3. This can be the case with some brands, and especially with the older generation models. The SevenPLUS that I use is more real-time than most - new results are displayed every 5 minutes, compared to Medtronic's 20 minutes (at least, the last I knew. They may have updated since the last time I checked them out.) There can definitely be a difference between your CGM readings and your finger stick readings - this is why they will tell you repeatedly during training that you CANNOT USE CGM RESULTS TO MAKE FOOD AND INSULIN DECISIONS. Now, granted - some of us do it anyway. :) It's really meant more to track your glucose trends, so you can understand what foods, insulin, exercise, stress, and everything else do to you. You'll still have to do finger sticks when wearing a CGM, but the CGM results sure do come in handy to help with fine-tuning.
4 (or, #3 again... ha). The "best" can only be determined by you. I would recommend that you do some research online, contact the companies that make the CGM devices you are interested in, and have them send you some packets of info. This will help you compare the different kinds side-by-side. Of course, I'm a little biased towards the Dexcom, because I love mine... not that I've never had problems with it, but the benefits have far outweighed the negatives for me. Also, the Medtronic CGM can be, or is only, integrated with their insulin pump - another thing to consider.
Best of luck! I hope this helps.