Clipless pedals/shoes make SO MUCH difference, especially when climbing or accelerating. Maybe not the best way to go if you do downhill or freestyle, but for XC or commuting, snapping in is definitely the way to go. I have 3 pairs of shoes. Work shoes (crusted with flour and sauce), a dressy pair I bought 3 days ago for a wedding I'll be at tomarrow, and some Shimano MT20Ds, which I wear everywhere, even when I'm not riding (I ride everywhere, I don't drive). They're normal looking and comfortable enough to wear as regular shoes. My old pair of Shimanos lasted more than 2 years of every-day use. Stay away from Specialized, mine fell apart (literally) in 5 months. I had a pair of Diadoras where the rubber on one shoe was thinner which made the cleat stick out too far and scrape everything.
Be careful with clipless shoes/pedals when you first start with them though. The twist in/out motion does not come naturally and takes a while to form the habit. In the meantime, you're going to fall over. A lot. Remember not to fall on your hand/wrist, or you could easily break it. Best to fall on your side (but not your shoulder--you could break that too). It's not a bad idea to practice in a park or other grassy area.
But really, going clipless is worth it for commuting or XC. Besides giving you extra power, it connects you to your bike in a way that turns you and the bike into a single unit, giving you more control and confidence. Plus, I never really felt that boot placement on the pedal with toe clips was really optimal; for me anyway. As Kohai said, you can get the combo platform/SPD pedals. My first clipless pedals were Shimano combo pedals. I figured that I wouldn't always be wearing my cycling shoes, so for quick jaunts, I'd just use the platforms and my regular shoes. But that changed once I got the hang of going clipless, because the difference it made was so huge that I never bothered wearing anything but my cycling shoes, and I switched to SPD only pedals.