I've never tried the mobile.weather.gov so I just checked it out. Yes it has the basic information, but it's not presented nearly as nice as accuweather.
Try to look at the forecast for the next 5 days to see high/low temps. With weather.gov, you need to scroll several screen because the high and low temperatures are each in a big block that takes 1/4 the screen, and your eyes have to wade through the day name, the overall condition name ("mostly sunny", "partly cloudy", etc) and a text description that is mostly redundant (most days it just repeats the overall condition name and the temp in sentence form, with some occasional extra info about chance of rain or whatever). Now try the same in accuweather. Easy. In a single screen I can see 6 whole days of forecast, no scrolling necesary. Further more, because it's in table format I can easily scan down the list of high/low temps without having to wade through any text. The condition graphics are a bit more meaningful. Its easier to see at a glance when rain is likely.
Now lets look at the radar. With the accuweather app it's easy because the common links are always at the top of the screen. On mobile.weather.gov you need to click back to get to the main screen, then scroll down to find the link to radar. Personally I also like the appearance/presentation of accuweather maps infinitely better...it looks nicer, you can zoom in better to see precisely where the rain is (or zoom out to get a better idea of whats a bit further away), and it filter out all the spurious radar blips/noise.
Same thing for hourly forecast...easier to access on accuweather because it's a tab at the top of every screen instead of having to find and drill down into the right block.
Now what if you like to check weather for multiple locations? On mobile.weather.gov you have to go back to the main screen, scroll back to the top, go to a different page to select your other location, then renavigate to what you were trying to check out. On accuweather you click an icon and a panel slides out with all your locations. Pick your new location and your are right back in the screen where you started. No navigation necessary
Finally a feature I love on accuweather....the 120 minute precipitation forecast. I find it very handy. I see nothing even remotely like it on mobile.weather.gov
So yeah, what you've got there is a totally free alternative that gives you most of the info, but it's not nearly as conveniently organized or as feature complete. If you like it, wonderful, but it shouldn't be a surprise that some people prefer the better packaging.