Ok, I think I have all your bases covered on this one. Don't bother with Nextel or T-Mobile, they suck. I used to be with Cingular... They do have the largest network now, but the drop calls all the time, and their customer service is horrendous.
I work for RadioShack, so I sell Verizon and Sprint. When it comes to the handsets, Sanyo are the highest rated in terms of quality and customer satisfaction. Despite the problems mentioned earlier in this thread, Samsung is actually right on the heels of Sanyo right now. I carry a Samsung, and I've actually had an experience with my phone that rivals that of what my collleagues have had with their Sanyo phones. My service is through Sprint, but quite honestly, I recommend Verizon. The main reason I go through Sprint instead of Verizon is that Sprint has by far the best data network out of everyone, so I can browse the internet on my phone, or use it as a wireless modem for my laptop. Avoid Sprint - you'll thank me in a couple years when you want to replace your phone. Unlike pretty much every other carrier, when you upgrade, instead of giving you new customer pricing, Sprint makes you pay full price unactivated price for the phone (often between, $200 and $300) and gives you a mail-in rebate for which you have to wait 6-8 weeks to get $150 back. It's completely ass-backwards.
Verizon has the second largest network, but their network is by far more reliable than any other out there. Also, their customer service is the best. Their plans start out at $39.99/mo., inclued unlimited In-Network calling, no roaming charges, ultd. nights & weekends, and incl. long distance. The nationwide plan at that price gets you 450 mins./mo., while the local version gets you 550. If you go up to the next plan, it's $59.99/mo., and it doubles you anytime minutes.
Quite honesly, cameras are slowly becoming a pretty standard feature in phones. If you want to get a decent phone, you're likely gonna end up getting one with a camera that you just won't use. One thing to look out for: If you're from a rural area or commute through a rural area, it is wise to make sure that your new phone will pick up both analog and digital signals. (Look for a dual-mode (Verizon) or tri-mode (Sprint) phone.)
No matter what phone you end up deciding on, odds are you'll find the best price on it at a RadioShack. I'm not just saying this because I work there (I actually hate the place and am just a few weeks away from quitting,) it's just the truth. 9 times out of 10, RadioShack will sell the phones for a lower price than Verizon Sales & Service Centers, or pretty much any other authorized retailer. If you do go to a RadioShack though, make sure you go to one where you know the people are smart, or go to one at a mall, since they will be the best trained and most experienced people to help you out.