Congrats on the new bike. I started with a Walmart bike many moons ago and I spent a couple of months on it till I realized I needed something a little better. That was many bikes ago lol. The only issue I have with a Walmart bike is not being able to get a good fit on it. This can turn people off of riding because it isn't real comfortable. You see people riding a Walmart bike and their seat is too low or they are too scrunched or stretched out and they don't know any better. Then they quit riding because the bike is uncomfortable.
Other then that I think its an okay place to start and see if riding is for you. This way you can ride it and decide on what riding style you like and what to look for in your next bike. Plus you can be riding while looking for something used to come along with a little more patience. Congrats again.