It _really_ depends on what you want to do with it. USB, by design, is a high-latency protocol. That means that with a scope, unless you use very fancy triggers with segmented capture and a _lot_ of sample memory, you will likely not capture enough time to decode to a higher protocol level.
USB, without higher-level decodes, is a lot of data to look at (and ignore), especially when there are multiple devices on the bus.
If you're after USB2.0 electrical compliance, a scope is probably the right tool, but a simple edge trigger will likely already do enough good.
If you're after USB "issues", and you can rule out electrical/PHY problems, then you don't need a scope and a USB protocol analyzer will do a far better job. I have used a few, but I liked the LeCroy the most (probably because I paid the most for them - sigh). YMMV, most of the others are also very good.
If you're after the combination, like "My device is randomly crashing after receiving a write command from host", your best bet is to augment your device with trigger outputs (for example, toggle a GPIO in the "write" command handler), and then you don't need USB decoding. If you can't (or don't want to) modify your DUT, use a USB protocol analyzer with trigger output to trigger a scope - most of the USB PAs can have really complex triggers that for most scenarios are flexible enough to trigger at a useful point.
The one thing where a USB decoder in the scope is really nice is when you want to learn about USB, which I feel works best by looking at the raw USB packets on the wire at least once. But that you can equally do with USB1.1.