Note that the software high marks refer to the older (grey) Novatel Connection Manager, not the newer black Sprint Connection Manager which I haven't tried.
I used to have an ancient Tmobile GPRS (not EDGE) data card, it was beat to hell (physically), slow (40kbit), unreliable (bad coverage), disconnected a lot. Figured EvDO would be a good upgrade, I was right! I borrowed one of these Novatel cards and knew it was what I needed within 30 seconds of using it.
The S720 is very well built and feels solid, even with the large block that sticks out the side of the laptop. While I wouldn't want to drop my laptop antenna-first, it feels like it will handle everyday abuse without cracking. So far I've not had any problems with the hardware, at all (and I've had it for about a year). It looks and feels quite a bit more solid than the Pantech card you can get for free, worth the extra $100 IMHO. I also don't think the Pantech card has GPS, the Novatel does.
Software installs nice and quick off the CD or sprint.com/downloads, I prefer the smaller/less bloated Novatel Connection Manager 3.x rather than the larger Sprint Connection Manger (black thing that also uses WiFi). After a few updates (totally automatic) you are good to go.
I configured my card for NDIS mode, so it shows up to Windows as an Ethernet adapter and connects immediately without having to launch the software. I just shove it in when I need it and 15 seconds later I'm online, no further action required. If I launch the software I can also get signal strength and enable the device's onboard GPS- it provides a standard NMEA output so it will work with DeLorme, MS Streets n Trips, or any other GPS mapping app. The connection manager also has a quick location find system where you can easily find the nearest gas/starbucks/hotel/etc via your favorite mapping site (google, live search, etc).
But the connection is what really shines. In my area there is EvDO Revision A (DoRA) service, and it tests at around 850-1000kbit download. It's fast. Really fast. I can be on my VPN, remote desktop'd to my main PC, while streaming music and surfing. If you need to get work done on the go, then this is for you. Having a separate datacard, while more expensive than using the phone as a modem, means you can talk and surf at the same time (a benefit that can be VERY useful).
Also the $60 unlimited data plan is actually unlimited. Verizon's 'unlimited' plan is limited at 5gbytes/mo of transfer, so if you use it too much your speed drops or they cancel your service. Not fun. Verizon also has a very restrictive terms of service- anything other than web/email/vpn is prohibited, no streaming, no youtube etc. It's not actually blocked, but the TOS is used to enforce the 5gb cap. Sprint's unlimited is actually unlimited and the TOS reflects that, no limits on streaming or what you can do with it. You can also get a router to go with this card; you put the card in the router and it becomes a mobile hotspot. With the router, any computer with a WiFi or Ethernet port can get on via your Sprint card, and you can have more than one computer online at once. This can make the Sprint service a good option for people who otherwise can't get cable or DSL.
I can't really review coverage as my coverage will differ from yours. Around here it's pretty good, DoRA everywhere. However some parts of the network only support EvDO Rev0 (around 450kbit/sec) or 1xRTT (80-120kbit/sec). You can also roam onto Verizon and many other carriers without extra fees; Verizon roaming is only at 1xRTT, Alltel allows EvDO though.
If you are considering the Sprint Mobile Broadband service, I highly recommend you give it a shot. Many Sprint stores (at least the ones around here) have a laptop set up with a mobile broadband card, so you can try out the speed. Also there is a 30 day guarantee so if you don't like it or don't get coverage where you need it you don't have to pay a big fee. And lastly I recommend the Novatel hardware over the other free stuff, it's worth the extra $100. You get GPS and (IMHO) a better built device. The Novatel 720 series includes PC card (this one), ExpressCard and USB devices so whatever flavor you need you're covered. Note that only the PC card works with the Linksys router Sprint sells; but other online stores sell routers that may work with the other devices.
Give this a shot. You won't be disappointed!