Welcome, welcome! The first bike I bought myself wasn't ultra cheap, but it was a $400 low-end Gary Fisher mountain bike. I loved the heck out of it and rode it everywhere. I think after a while I just felt the need for speed and mountain bikes are fairly specialized. I started shopping around for a real road bike two years later. It was the rode bike that really changed the way I was riding around... and some days I really miss those leisurely "Townie" style rides that aren't all ridiculously hard work all the time. I'm glad I went down that road though, because I love what hard road biking and hard mountain biking do for my health and energy levels. Plus I feel a great sense of accomplishment in many different aspects of cycling.

Generally speaking, you pay more for the quality of the bike components and when you spend more money, it makes a big difference when it comes to ease of shifting/braking, frequency of required maintenance and durability. You also start seeing the weight of bikes drop off fairly sharply.

Anyway, if you love it on a bike that is not the greatest, then think how much you'll love it when you upgrade eventually!