DW and I both have Nextels, I have an i830, and she has the i860. I've had mine about 2 years now and not had a single problem with it (so I'm, not sure what the Nextel guy was talking about) The thing I like about mine is that it fits in one of those little blizzard beach water tight cases (including a few bucks, credit cards, beach/pool/annual passes)
The i860 is neat if you like the camera phone feature, but it feels cheaper than the 830.
As for plans I have a National Incoming 400 plan, with Nationwide direct connect (400cell min, unlimited nationwide DC, long dist. included, free nights and weekends, free incoming calls)
If you REALLY look at the share plans they don't save you anything - they actually cost more...my wife works at a car dealership and the rep that handles all of their phones told her to stay away from those plans.
ALSO - very important - if you or your SO work for a large enough company you can "guilt by assosciation" yourself into a corporate discount...my company has thousands of nextel accounts and phones, I get an additional 20% off my personal (not used for, or paid by work) Nextel bill, and 39% off phones and accessories. This applies to all phones on the account, and since DW works for a car dealership, she would've been entitled to a discount anyway - and get this -it is not based off her company, but the auto manufecturer they are associated with, but my co.'s discount was still better.
THe most important thing to remember when picking a plan is the minutes you'll use and then the price difference between the step up to the next plan vs. cash paying any overage in minutes. Also, does NExtel DC work for you and your calling circle of friends/family...ALL of my family and friends have Nextels - I have not gone over my 400 minutes at all - close but never over.