I got one with my bike; the shop put a bunch of zip ties to run it along the bottom of the downtube. But that looked a bit tacky for such a sexy bike, and against my better judgment, I took it back and got the wireless one. I've heard a lot about this being less reliable than the wired version, although after 200 miles, I haven't seen an issue. The folks at the bike shop said it'll lose the signal for a split second every now and then, but rarely.
The speed is displayed in a pretty large font, and the second display is kind of small. I typically leave it on cadence, and have no trouble reading the display (except at night). The cadence lags a second behind reality, on the wired and wireless version.
I really like the two distance settings in the Strada; one tells me how many miles I've gone that day, and the other for the week. You can reset them whenever you'd like, but I like knowing my mileage per week or per month, without having to keep track of things and add up a column of numbers. I didn't think I'd use that, but it turns out it's really nice to have.