Verizon 4510L detailed review
I have been using the Verizon Mifi 2200 (3g) for 2 years and had been pleased with it. My contract was up in August so I was looking to upgrade to a 4G hotspot. The 2200 was a decent hotspot, and Verizon 3G was around 400kbps to 1.2Mbps depending on signal, location, people around, etc. It was acceptable for most web access but downloading files and streaming media was not optimal.
The 4510L fixes just about every gripe I had with the 2200 functionally. The 2200 would not power off when plugged in - the 4510L does. The indicator screen is a nice addition. The 2200 you had to go to the web page configuration to see battery, signal strength, and number of devices connected. All of those are now shown on a screen on the top of the device. The LED also tells you if you are on 3G (turns purple) 4G (turns green) and if data is being used. That way you don't have to go to a device and go to a web page just to see how the battery is doing.
I had bought an extended battery for the 2200 and that lasted 10-12 hours. I bought the extended battery as mentioned above for the 4510L and it seems to do 10-12 as well. I have used it for 8 hours and still had 2 bars of battery left - so I am extrapolating. Either way - I just turn it on in the morning and let it run all day. It does mean that an iPad and iPhone are constantly connected and all the data usage that entails.
The 4G - when you can get it has been quite good. I usually get around 3-4Mbps (up and down) but have seen it go to 1.6Mbps when in a crowded area. Coverage is of course key, but there is 3G in a lot of places, and 4G in Denver and Colorado Springs - which is where I will be using the device the most. Verizon is claiming 9Mbps average but I haven't come close to that with the speed tests I've run. It drops to 3G fine and I still see the 400kbps to 1Mbps when using the 3G network.
Streaming videos on youtube, and music from Napster have had no problems. Netflix also streams pretty well. FaceTime and Skype video calling also worked and didn't pixelate too badly.
Downside is the price of data - $80/10GB/month - and $10/GB over is pretty steep. Plus with 4G it is really easy to get to 10GB fast. If this data cap were more reasonable - and I didn't have an entire family using computers, I would consider getting rid of my cable and just use Verizon 4G. As it is - 10GB/month is a pretty low cap especially with a netflix and napster subscription.
Another upside - is battery life - for devices. Because I am now using wifi data instead of onboard 3g data - the battery life of my iPhone seems better. Also I didn't get the 3G iPad but talking to some friends it sounds like 3G data drops battery life by ~20% (i.e. 8hrs instead of 10hrs) So that is all isolated from my devices.
Yet another upside is I have a WPA2-AES secure wireless network - so I can do stuff like displaypad between the computer and the iPad, snatch mouse from iPhone to computer, and anything else that needs a LAN.
TL ; DR - If you are a mobile user and need data everywhere, a wifi access point with a big battery can provide data all day long to all your devices but at a premium cost for data.