Monitors are not required to offer a lot of extra ports when they're cheap, but as the price rises beyond a few hundred dollars, extra connections become expected. Apple has a reputation for poor connectivity compared to similarly priced competitors, and while the Thunderbolt display does buck the trend somewhat, it could be better.
The main connectivity feature, the Thunderbolt port, is in effect nothing more than Mini DisplayPort. Thunderbolt's more attractive feature is its bandwidth, but that doesn't offer any advantage here. It's also possible to daisy-chain multiple Thunderbolt devices using a single port, but given the lack of compatible devices currently on the market, it's hard to imagine this advantage being commonly used. The only common application I can think of is daisy-chaining two displays to a single MacBook Pro, which is said to be possible (I have not tested it personally).
You'll also receive 3 USB 2.0 ports, a FireWire 800 port, and an Ethernet port. These ports can act as extensions of the connected Mac, which is handy in some cases. MacBook Airs, for example, don't have Ethernet available even as an option, but can use an Ethernet connection via this display.
What's lacking is, of course, HDMI and DVI. The lack of USB 3.0 ports is also a downer, though many competitors have yet to offer USB 3.0 as well. The connections available on the Thunderbolt display makes sense if you are connecting it to a Mac, but if you aren't, it's going to seem rather limited.