Juniper is very popular among big ISPs. I remember taking a walk through a very large DC in San Jose California, and I reckon I saw more Juniper kit in there than Cisco.
Even if you dont "switch" from Cisco to Juniper, being multi skilled in multiple vendors can only be good for you when it comes to job hunting. That might be the edge you have over the other guys...
I picked up my first Juniper router back in 2008 or so, just a lowly J2300, and compared to traditional IOS, JunOS blows Cisco way out of the water, especially from a configuration point of view.
If you want something new and cheap, the SRX line is quite competitively priced. I picked up a SRX100B for a little over AUD$500, brand new. It runs all of the latest JunOS versions, whereas my J2300 is limited to 9.3. Newer J series (like the J2320, basically anything thats not a Jx300) also run the latest images but are a bit more expensive.
Still, its good for getting a foot in the door, and I still use my J2300 in my lab. Looking at picking up an M7i or two soon, logical systems are a really intriguing feature, allowing you to run up to 15 individual routers on a single box, very much like a VM. Good for building complex topologies without the mess!