Sr-90 is can be a long-term hazard if it is not properly isolated because it has a high biological uptake and is a strong beta emitter which can cause bone cancer if it is absorbed. Thus it is often considered one of the more nasty fission products in a fallout situation.
It's half-life is one of the "intermediate" ones. In other words, it's short enough to be highly radioactive, but long enough that it won't just decay in a short period of time.
HOWEVER:
When isolated and encapsulated or otherwise bonded into a chemically inert material it is about the best beta emitter around. It emits strictly beta radiation and it does it twice over by it's daughter product. In large quantities it can even provide significant heat.
As far as gamma, yes, it can produce some X-rays as any strong beta emitter can. That depends a lot on the configuration of the source and what other materials are around it. In general, the small amount of X-rays it produces are not hard to shield against (well maybe if you have a hell of a lot of it).
My general experience with the stuff is that it doesn't produce much appreciable gamma from the rare isomer decay that occasionally is observed.
Yes, I have some Sr-90. No, don't go call the authorities. It's not license bearing.
I have a couple of check sources which I got through an NRC-approved company under license-exempt provisions and quantities.
If you'd like to buy some I can get you some too. It's also available here:
http://www.unitednuclear.com/isotopes.htm
But be a pal and buy it from me instead and I'll cut you a deal and I can also get it in slightly higher quantities per source, for a bit more. The limit is about .5 uCi, so sorry if anyone